Java ArrayList中的ArrayList项会重复

我正在制作一个GUI来存储每个产品的产品（ArrayList）和产品项（ArrayList）。但是，当我保存时，Arraylist项会发生更改，最近保存的项会在整个Arraylist中重复出现

我希望输出为（第二次保存时）：

但事实是：

[[2, TEST2, TEST2, TEST2, TEST2, TEST2, 2021-02-27], [2, TEST2, TEST2, TEST2, TEST2, TEST2, 2021-02-27]]

有什么我遗漏的吗？任何帮助都将不胜感激

我的代码：

package prog2exer1;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.table.DefaultTableModel;
import java.util.ArrayList;


public class Products extends javax.swing.JFrame {
 
          Date currentDate = new Date();
          DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
          String strDate = dateFormat.format(currentDate);
          ArrayList<ArrayList<String>> contentItems = new ArrayList();
          ArrayList<String> contents = new ArrayList();
          int id = 1;

    public Products() {
        initComponents();
        dateReceieved.setText(strDate);
        pID.setText(Integer.toString(id));
        DefaultTableModel tblmodel = (DefaultTableModel) products.getModel();
        tblmodel.setRowCount(0);
    }

  
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jLabel6 = new javax.swing.JLabel();
        jLabel7 = new javax.swing.JLabel();
        jLabel8 = new javax.swing.JLabel();
        pID = new javax.swing.JTextField();
        pType = new javax.swing.JTextField();
        pDesc = new javax.swing.JTextField();
        pSupplier = new javax.swing.JTextField();
        quantityTrue = new javax.swing.JTextField();
        pCost = new javax.swing.JTextField();
        dateReceieved = new javax.swing.JTextField();
        jLabel9 = new javax.swing.JLabel();
        plusSign = new javax.swing.JLabel();
        quantityAdd = new javax.swing.JTextField();
        jPanel1 = new javax.swing.JPanel();
        jScrollPane1 = new javax.swing.JScrollPane();
        products = new javax.swing.JTable();
        jPanel2 = new javax.swing.JPanel();
        jScrollPane2 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();
        newProduct = new javax.swing.JButton();
        stockIn = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setText("Product ID");

        jLabel2.setText("Product Type");

        jLabel3.setText("Product Description");

        jLabel4.setText("Supplier");

        jLabel6.setText("Quantity");

        jLabel7.setText("Total Cost");

        jLabel8.setText("Date Received");

        pID.setEditable(false);

        dateReceieved.setEditable(false);

        jLabel9.setFont(new java.awt.Font("Dialog", 1, 18)); // NOI18N
        jLabel9.setText("New Products Stock-in");

        plusSign.setText("+");

        products.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null, null, null},
                {null, null, null, null, null, null},
                {null, null, null, null, null, null},
                {null, null, null, null, null, null}
            },
            new String [] {
                "ID", "pType", "pDesc", "Supplier", "Total Quantity", "Orders"
            }
        ));
        products.setCellSelectionEnabled(true);
        products.setFocusTraversalPolicyProvider(true);
        products.setName(""); // NOI18N
        jScrollPane1.setViewportView(products);
        products.getColumnModel().getSelectionModel().setSelectionMode(javax.swing.ListSelectionModel.SINGLE_INTERVAL_SELECTION);

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 735, Short.MAX_VALUE)
                .addContainerGap())
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 228, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(193, 193, 193))
        );

        jTable1.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null, null, null, null, null},
                {null, null, null, null, null, null, null, null},
                {null, null, null, null, null, null, null, null},
                {null, null, null, null, null, null, null, null}
            },
            new String [] {
                "ID", "PType", "PDesc", "Supplier", "Quantity", "Cost", "Date Received", "Orders"
            }
        ));
        jScrollPane2.setViewportView(jTable1);

        javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
        jPanel2.setLayout(jPanel2Layout);
        jPanel2Layout.setHorizontalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane2, javax.swing.GroupLayout.DEFAULT_SIZE, 721, Short.MAX_VALUE)
                .addContainerGap())
        );
        jPanel2Layout.setVerticalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 411, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(16, Short.MAX_VALUE))
        );

        newProduct.setText("New Product");
        newProduct.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                newProductActionPerformed(evt);
            }
        });

        stockIn.setText("Stock In");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(27, 27, 27)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createSequentialGroup()
                                .addComponent(jLabel6)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(quantityTrue, javax.swing.GroupLayout.PREFERRED_SIZE, 82, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(plusSign, javax.swing.GroupLayout.PREFERRED_SIZE, 17, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(quantityAdd))
                            .addGroup(layout.createSequentialGroup()
                                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                    .addGroup(layout.createSequentialGroup()
                                        .addComponent(jLabel3)
                                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                        .addComponent(pDesc, javax.swing.GroupLayout.PREFERRED_SIZE, 124, javax.swing.GroupLayout.PREFERRED_SIZE))
                                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel7)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(pCost))
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel4)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(pSupplier, javax.swing.GroupLayout.PREFERRED_SIZE, 119, javax.swing.GroupLayout.PREFERRED_SIZE))
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel2)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(pType))
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel1)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(pID, javax.swing.GroupLayout.PREFERRED_SIZE, 138, javax.swing.GroupLayout.PREFERRED_SIZE))
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel8)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(dateReceieved)))
                                    .addComponent(stockIn)
                                    .addComponent(newProduct))
                                .addGap(0, 0, Short.MAX_VALUE))))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(83, 83, 83)
                        .addComponent(jLabel9)))
                .addGap(118, 118, 118)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(6, 6, 6)
                        .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addContainerGap(50, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(36, 36, 36)
                .addComponent(jLabel9)
                .addGap(30, 30, 30)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel1)
                            .addComponent(pID, javax.swing.GroupLayout.PREFERRED_SIZE, 24, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel2)
                            .addComponent(pType))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel3)
                            .addComponent(pDesc))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel4)
                            .addComponent(pSupplier))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel6)
                            .addComponent(quantityTrue)
                            .addComponent(plusSign, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(quantityAdd))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel7)
                            .addComponent(pCost))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel8)
                            .addComponent(dateReceieved))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(newProduct)
                        .addGap(4, 4, 4)
                        .addComponent(stockIn)
                        .addGap(560, 560, 560))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, 240, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))))
        );

        pack();
    }// </editor-fold>                        

    private void newProductActionPerformed(java.awt.event.ActionEvent evt) {                                           
        DefaultTableModel tblmodel = (DefaultTableModel) products.getModel();
        
        contents.clear();
        
        contents.add(pID.getText());
        contents.add(pType.getText());
        contents.add(pDesc.getText());
        contents.add(pSupplier.getText());
        contents.add(quantityTrue.getText());
        contents.add(pCost.getText());
        contents.add(strDate);
                
        contentItems.add(contents);
        
        System.out.println(contents);
        System.out.println(contentItems);
        
        pID.setText(Integer.toString(id));
       id++;
       
    }                                          


    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Products().setVisible(true);
                
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JTextField dateReceieved;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JLabel jLabel7;
    private javax.swing.JLabel jLabel8;
    private javax.swing.JLabel jLabel9;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JTable jTable1;
    private javax.swing.JButton newProduct;
    private javax.swing.JTextField pCost;
    private javax.swing.JTextField pDesc;
    private javax.swing.JTextField pID;
    private javax.swing.JTextField pSupplier;
    private javax.swing.JTextField pType;
    private javax.swing.JLabel plusSign;
    private javax.swing.JTable products;
    private javax.swing.JTextField quantityAdd;
    private javax.swing.JTextField quantityTrue;
    private javax.swing.JButton stockIn;
    // End of variables declaration                   


}

包prog2exer1；
导入java.text.DateFormat；
导入java.text.simpleDataFormat；
导入java.util.Date；
导入javax.swing.table.DefaultTableModel；
导入java.util.ArrayList；
公共类产品扩展了javax.swing.JFrame{
日期currentDate=新日期（）；
DateFormat DateFormat=新的简化格式（“yyyy-MM-dd”）；
字符串strDate=dateFormat.format（currentDate）；
ArrayList contentItems=新的ArrayList（）；
ArrayList contents=新的ArrayList（）；
int-id=1；
公共产品（）{
初始化组件（）；
datereceived.setText（标准日期）；
setText（Integer.toString（id））；
DefaultTableModel tblmodel=（DefaultTableModel）products.getModel（）；
tblmodel.setRowCount（0）；
}
@抑制警告（“未选中”）
//                           
私有组件（）{
jLabel1=newjavax.swing.JLabel（）；
jLabel2=newjavax.swing.JLabel（）；
jLabel3=newjavax.swing.JLabel（）；
jLabel4=newjavax.swing.JLabel（）；
jLabel6=newjavax.swing.JLabel（）；
jLabel7=newjavax.swing.JLabel（）；
jLabel8=newjavax.swing.JLabel（）；
pID=newjavax.swing.JTextField（）；
pType=newjavax.swing.JTextField（）；
pDesc=newjavax.swing.JTextField（）；
pSupplier=newjavax.swing.JTextField（）；
quantityTrue=newjavax.swing.JTextField（）；
pCost=newjavax.swing.JTextField（）；
DateReceived=newjavax.swing.JTextField（）；
jLabel9=newjavax.swing.JLabel（）；
plusSign=newjavax.swing.JLabel（）；
quantityAdd=newjavax.swing.JTextField（）；
jPanel1=newjavax.swing.JPanel（）；
jScrollPane1=newjavax.swing.JScrollPane（）；
products=newjavax.swing.JTable（）；
jPanel2=newjavax.swing.JPanel（）；
jScrollPane2=newjavax.swing.JScrollPane（）；
jTable1=newjavax.swing.JTable（）；
newProduct=newjavax.swing.JButton（）；
stockIn=newjavax.swing.JButton（）；
setDefaultCloseOperation（javax.swing.WindowConstants.EXIT_ON_CLOSE）；
jLabel1.setText（“产品ID”）；
jLabel2.setText（“产品类型”）；
jLabel3.setText（“产品说明”）；
jLabel4.setText（“供应商”）；
jLabel6.setText（“数量”）；
jLabel7.setText（“总成本”）；
jLabel8.setText（“收到日期”）；
pID.setEditable（假）；
DateReceived.setEditable（false）；
jLabel9.setFont（新的java.awt.Font（“Dialog”，1，18））；//NOI18N
jLabel9.setText（“新产品库存”）；
plusSign.setText（“+”）；
products.setModel（新的javax.swing.table.DefaultTableModel(
新对象[][]{
{null，null，null，null，null，null，null}，
{null，null，null，null，null，null，null}，
{null，null，null，null，null，null，null}，
{null，null，null，null，null，null，null}
},
新字符串[]{
“ID”、“P类型”、“pDesc”、“供应商”、“总数量”、“订单”
}
));
products.setCellSelectionEnabled（真）；
产品.setFocusTraversalPolicyProvider（真）；
products.setName（“”；//NOI18N
jScrollPane1.setViewportView（产品）；
products.getColumnModel（）.getSelectionModel（）.setSelectionMode（javax.swing.ListSelectionModel.SINGLE\u INTERVAL\u SELECTION）；
javax.swing.GroupLayout jPanel1Layout=新的javax.swing.GroupLayout（jPanel1）；
setLayout（jPanel1Layout）；
jPanel1Layout.setHorizontalGroup(
jPanel1Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（jpanellayout.createSequentialGroup（）
.addContainerGap（）
.addComponent（jScrollPane1，javax.swing.GroupLayout.DEFAULT\u SIZE，735，Short.MAX\u值）
.addContainerGap（））
);
jPanel1Layout.setVerticalGroup(
jPanel1Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（javax.swing.GroupLayout.Alignment.TRAILING，jPanel1Layout.createSequentialGroup（）
.addContainerGap（javax.swing.GroupLayout.DEFAULT\u SIZE，Short.MAX\u值）
.addComponent（jScrollPane1，javax.swing.GroupLayout.PREFERRED\u SIZE，228，javax.swing.GroupLayout.PREFERRED\u SIZE）
.addGap（193193193193））
);
jTable1.setModel（新的javax.swing.table.DefaultTableModel(
新对象[][]{
{null，null，null，null，null，null，null，null，null，null}，
{null，null，null，null，null，null，null，null，null，null}，
{null，null，null，null，null，null，null，null，null，null}，
{null，null，null，null，null，null，null，null，null，null}
},
新字符串[]{
“ID”、“P类型”、“PDesc”、“供应商”、“数量”、“成本”、“收到日期”、“订单”
}
));
jScrollPane2.setViewportView（jTable1）；
javax.swing.GroupLayout jPanel2Layout=新的javax.swing.GroupLayout（jPanel2）；
设置布局（jPanel2布局）；
jPanel2Layout.setHorizontalGroup(
jPanel2Layout.createParallelGroup（javax.swing.GroupLayout.Alignment.LEADING）
.addGroup（jPanel2Layout.createSequentialGroup（）
.addContainerGap（）
.addComponent（jScrollPane2，javax.swing.GroupLayout.DEFAULT\u SIZE，721，Short.MAX\u值）
.addContainerGap（））
);
jPanel2Layout.setVertical
package prog2exer1;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import javax.swing.table.DefaultTableModel;
import java.util.ArrayList;


public class Products extends javax.swing.JFrame {
 
          Date currentDate = new Date();
          DateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
          String strDate = dateFormat.format(currentDate);
          ArrayList<ArrayList<String>> contentItems = new ArrayList();
          ArrayList<String> contents = new ArrayList();
          int id = 1;

    public Products() {
        initComponents();
        dateReceieved.setText(strDate);
        pID.setText(Integer.toString(id));
        DefaultTableModel tblmodel = (DefaultTableModel) products.getModel();
        tblmodel.setRowCount(0);
    }

  
    @SuppressWarnings("unchecked")
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {

        jLabel1 = new javax.swing.JLabel();
        jLabel2 = new javax.swing.JLabel();
        jLabel3 = new javax.swing.JLabel();
        jLabel4 = new javax.swing.JLabel();
        jLabel6 = new javax.swing.JLabel();
        jLabel7 = new javax.swing.JLabel();
        jLabel8 = new javax.swing.JLabel();
        pID = new javax.swing.JTextField();
        pType = new javax.swing.JTextField();
        pDesc = new javax.swing.JTextField();
        pSupplier = new javax.swing.JTextField();
        quantityTrue = new javax.swing.JTextField();
        pCost = new javax.swing.JTextField();
        dateReceieved = new javax.swing.JTextField();
        jLabel9 = new javax.swing.JLabel();
        plusSign = new javax.swing.JLabel();
        quantityAdd = new javax.swing.JTextField();
        jPanel1 = new javax.swing.JPanel();
        jScrollPane1 = new javax.swing.JScrollPane();
        products = new javax.swing.JTable();
        jPanel2 = new javax.swing.JPanel();
        jScrollPane2 = new javax.swing.JScrollPane();
        jTable1 = new javax.swing.JTable();
        newProduct = new javax.swing.JButton();
        stockIn = new javax.swing.JButton();

        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);

        jLabel1.setText("Product ID");

        jLabel2.setText("Product Type");

        jLabel3.setText("Product Description");

        jLabel4.setText("Supplier");

        jLabel6.setText("Quantity");

        jLabel7.setText("Total Cost");

        jLabel8.setText("Date Received");

        pID.setEditable(false);

        dateReceieved.setEditable(false);

        jLabel9.setFont(new java.awt.Font("Dialog", 1, 18)); // NOI18N
        jLabel9.setText("New Products Stock-in");

        plusSign.setText("+");

        products.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null, null, null},
                {null, null, null, null, null, null},
                {null, null, null, null, null, null},
                {null, null, null, null, null, null}
            },
            new String [] {
                "ID", "pType", "pDesc", "Supplier", "Total Quantity", "Orders"
            }
        ));
        products.setCellSelectionEnabled(true);
        products.setFocusTraversalPolicyProvider(true);
        products.setName(""); // NOI18N
        jScrollPane1.setViewportView(products);
        products.getColumnModel().getSelectionModel().setSelectionMode(javax.swing.ListSelectionModel.SINGLE_INTERVAL_SELECTION);

        javax.swing.GroupLayout jPanel1Layout = new javax.swing.GroupLayout(jPanel1);
        jPanel1.setLayout(jPanel1Layout);
        jPanel1Layout.setHorizontalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel1Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane1, javax.swing.GroupLayout.DEFAULT_SIZE, 735, Short.MAX_VALUE)
                .addContainerGap())
        );
        jPanel1Layout.setVerticalGroup(
            jPanel1Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(javax.swing.GroupLayout.Alignment.TRAILING, jPanel1Layout.createSequentialGroup()
                .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addComponent(jScrollPane1, javax.swing.GroupLayout.PREFERRED_SIZE, 228, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(193, 193, 193))
        );

        jTable1.setModel(new javax.swing.table.DefaultTableModel(
            new Object [][] {
                {null, null, null, null, null, null, null, null},
                {null, null, null, null, null, null, null, null},
                {null, null, null, null, null, null, null, null},
                {null, null, null, null, null, null, null, null}
            },
            new String [] {
                "ID", "PType", "PDesc", "Supplier", "Quantity", "Cost", "Date Received", "Orders"
            }
        ));
        jScrollPane2.setViewportView(jTable1);

        javax.swing.GroupLayout jPanel2Layout = new javax.swing.GroupLayout(jPanel2);
        jPanel2.setLayout(jPanel2Layout);
        jPanel2Layout.setHorizontalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane2, javax.swing.GroupLayout.DEFAULT_SIZE, 721, Short.MAX_VALUE)
                .addContainerGap())
        );
        jPanel2Layout.setVerticalGroup(
            jPanel2Layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(jPanel2Layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(jScrollPane2, javax.swing.GroupLayout.PREFERRED_SIZE, 411, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addContainerGap(16, Short.MAX_VALUE))
        );

        newProduct.setText("New Product");
        newProduct.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                newProductActionPerformed(evt);
            }
        });

        stockIn.setText("Stock In");

        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(27, 27, 27)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(layout.createSequentialGroup()
                                .addComponent(jLabel6)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(quantityTrue, javax.swing.GroupLayout.PREFERRED_SIZE, 82, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addGap(18, 18, 18)
                                .addComponent(plusSign, javax.swing.GroupLayout.PREFERRED_SIZE, 17, javax.swing.GroupLayout.PREFERRED_SIZE)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(quantityAdd))
                            .addGroup(layout.createSequentialGroup()
                                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                    .addGroup(layout.createSequentialGroup()
                                        .addComponent(jLabel3)
                                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                        .addComponent(pDesc, javax.swing.GroupLayout.PREFERRED_SIZE, 124, javax.swing.GroupLayout.PREFERRED_SIZE))
                                    .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel7)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(pCost))
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel4)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(pSupplier, javax.swing.GroupLayout.PREFERRED_SIZE, 119, javax.swing.GroupLayout.PREFERRED_SIZE))
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel2)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(pType))
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel1)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(pID, javax.swing.GroupLayout.PREFERRED_SIZE, 138, javax.swing.GroupLayout.PREFERRED_SIZE))
                                        .addGroup(javax.swing.GroupLayout.Alignment.LEADING, layout.createSequentialGroup()
                                            .addComponent(jLabel8)
                                            .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                            .addComponent(dateReceieved)))
                                    .addComponent(stockIn)
                                    .addComponent(newProduct))
                                .addGap(0, 0, Short.MAX_VALUE))))
                    .addGroup(layout.createSequentialGroup()
                        .addGap(83, 83, 83)
                        .addComponent(jLabel9)))
                .addGap(118, 118, 118)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGroup(layout.createSequentialGroup()
                        .addGap(6, 6, 6)
                        .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)))
                .addContainerGap(50, Short.MAX_VALUE))
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(36, 36, 36)
                .addComponent(jLabel9)
                .addGap(30, 30, 30)
                .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(layout.createSequentialGroup()
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel1)
                            .addComponent(pID, javax.swing.GroupLayout.PREFERRED_SIZE, 24, javax.swing.GroupLayout.PREFERRED_SIZE))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel2)
                            .addComponent(pType))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel3)
                            .addComponent(pDesc))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel4)
                            .addComponent(pSupplier))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel6)
                            .addComponent(quantityTrue)
                            .addComponent(plusSign, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                            .addComponent(quantityAdd))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel7)
                            .addComponent(pCost))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addGroup(layout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(jLabel8)
                            .addComponent(dateReceieved))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(newProduct)
                        .addGap(4, 4, 4)
                        .addComponent(stockIn)
                        .addGap(560, 560, 560))
                    .addGroup(layout.createSequentialGroup()
                        .addComponent(jPanel1, javax.swing.GroupLayout.PREFERRED_SIZE, 240, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addComponent(jPanel2, javax.swing.GroupLayout.PREFERRED_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.PREFERRED_SIZE)
                        .addContainerGap(javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE))))
        );

        pack();
    }// </editor-fold>                        

    private void newProductActionPerformed(java.awt.event.ActionEvent evt) {                                           
        DefaultTableModel tblmodel = (DefaultTableModel) products.getModel();
        
        contents.clear();
        
        contents.add(pID.getText());
        contents.add(pType.getText());
        contents.add(pDesc.getText());
        contents.add(pSupplier.getText());
        contents.add(quantityTrue.getText());
        contents.add(pCost.getText());
        contents.add(strDate);
                
        contentItems.add(contents);
        
        System.out.println(contents);
        System.out.println(contentItems);
        
        pID.setText(Integer.toString(id));
       id++;
       
    }                                          


    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Products().setVisible(true);
                
            }
        });
    }

    // Variables declaration - do not modify                     
    private javax.swing.JTextField dateReceieved;
    private javax.swing.JLabel jLabel1;
    private javax.swing.JLabel jLabel2;
    private javax.swing.JLabel jLabel3;
    private javax.swing.JLabel jLabel4;
    private javax.swing.JLabel jLabel6;
    private javax.swing.JLabel jLabel7;
    private javax.swing.JLabel jLabel8;
    private javax.swing.JLabel jLabel9;
    private javax.swing.JPanel jPanel1;
    private javax.swing.JPanel jPanel2;
    private javax.swing.JScrollPane jScrollPane1;
    private javax.swing.JScrollPane jScrollPane2;
    private javax.swing.JTable jTable1;
    private javax.swing.JButton newProduct;
    private javax.swing.JTextField pCost;
    private javax.swing.JTextField pDesc;
    private javax.swing.JTextField pID;
    private javax.swing.JTextField pSupplier;
    private javax.swing.JTextField pType;
    private javax.swing.JLabel plusSign;
    private javax.swing.JTable products;
    private javax.swing.JTextField quantityAdd;
    private javax.swing.JTextField quantityTrue;
    private javax.swing.JButton stockIn;
    // End of variables declaration                   


}

 private void newProductActionPerformed(java.awt.event.ActionEvent evt) {                                           
        DefaultTableModel tblmodel = (DefaultTableModel) products.getModel();
        
        contents.clear(); // wrong, you are using same content object...
        contents = new ArrayList();// create new object for each content