有人知道为什么抛出此异常吗？“线程中的异常”；AWT-EventQueue-0“；java.lang.NullPointerException
可能重复：有人知道为什么抛出此异常吗？“线程中的异常”；AWT-EventQueue-0“；java.lang.NullPointerException,java,exception,nullpointerexception,awt,rollover,Java,Exception,Nullpointerexception,Awt,Rollover,可能重复： 问题是这个语句在一个名为body的方法中太长了，我无法添加它 else { tableButton = new JButton("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."); } } tableButton为空，除非运行了if/else if/else长列表中的else部分 换句话说，如果wbTemp介于69和82之间，
问题是这个语句在一个名为body的方法中太长了，我无法添加它
else
{
tableButton = new JButton("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables.");
}
}
tableButtonifelse ifelseelsewbTempwbTemptableButton=newjbutton（…）- 如果条件1为true，则只运行块1
- 如果条件1为false而条件2为true，则只运行块2
- 如果条件1为false，条件2为false，则只运行块3
请在
SelectUnitFrametableButtonsetRolloverEnablednulltableButton=new JButton（“冷却塔无法处理湿球中的温度”）
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
public class SelectUnitFrame extends JFrame
{
public JLabel showNumbersLabel;
public JPanel showPanel = new JPanel();
public JButton tableButton;
public JPanel buttonPanel = new JPanel();
public JButton goBackButton = new JButton("Change Variables");
public JButton exitButton = new JButton("Done");
public JButton nextButton = new JButton(">");
public JButton prevButton = new JButton("<");
public int fRate;
public int wbTemp;
public int r;
public int a;
public int rcTons;
public int count;
public String [] tablesFor80 = {"80F_FG2003.GIF", "80F_FG2004.GIF", "80F_FG2005.GIF", "80F_FG2007.GIF", "80F_FG2009.GIF", "80F_FG2011.GIF", "80F_FG2015.GIF"};
public String [] tablesFor78 = {"78F_FG2003.GIF", "78F_FG2004.GIF", "78F_FG2005.GIF", "78F_FG2007.GIF", "78F_FG2009.GIF", "78F_FG2011.GIF", "78F_FG2015.GIF"};
public String [] tablesFor76 = {"76F_FG2003.GIF", "76F_FG2004.GIF", "76F_FG2005.GIF", "76F_FG2007.GIF", "76F_FG2009.GIF", "76F_FG2011.GIF", "76F_FG2015.GIF"};
public String [] tablesFor74 = {"74F_FG2003.GIF", "74F_FG2004.GIF", "74F_FG2005.GIF", "74F_FG2007.GIF", "74F_FG2009.GIF", "74F_FG2011.GIF", "74F_FG2015.GIF"};
public String [] tablesFor72 = {"72F_FG2003.GIF", "72F_FG2004.GIF", "72F_FG2005.GIF", "72F_FG2007.GIF", "72F_FG2009.GIF", "72F_FG2011.GIF", "72F_FG2015.GIF"};
public String [] tablesFor70 = {"70F_FG2003.GIF", "70F_FG2004.GIF", "70F_FG2005.GIF", "70F_FG2007.GIF", "70F_FG2009.GIF", "70F_FG2011.GIF", "70F_FG2015.GIF"};
public String [] tablesFor68 = {"68F_FG2003.GIF", "68F_FG2004.GIF", "68F_FG2005.GIF", "68F_FG2007.GIF", "68F_FG2009.GIF", "68F_FG2011.GIF", "68F_FG2015.GIF"};
public ImageIcon tablePicture;
public SelectUnitFrame(int flowRate, int wetBulbTemp, int roundedCoolingTons, int approach, int range)
{
super("Unit Selected");
Toolkit toolkit = Toolkit.getDefaultToolkit();
Dimension dimensions = toolkit.getScreenSize();
int x = (dimensions.width - 750)/2;
int y = (dimensions.height - 350)/2;
setBounds(x, y, 750, 350);
setVisible(true);
setResizable(false);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
goBackButton.addActionListener(new ButtonListener());
exitButton.addActionListener(new ButtonListener());
nextButton.addActionListener(new ButtonListener());
prevButton.addActionListener(new ButtonListener());
fRate = flowRate;
wbTemp = wetBulbTemp;
r = range;
a = approach;
rcTons = roundedCoolingTons;
buttonPanel.add(goBackButton);
buttonPanel.add(exitButton);
add(buttonPanel, BorderLayout.SOUTH);
showNumbersLabel = new JLabel("Wet Bulb: " + wbTemp + "(deg)F " + "Range: " + r + " Approach: " + a + " Tons/GPM: " + rcTons + "/" + fRate);
showPanel.add(showNumbersLabel);
add(showPanel, BorderLayout.NORTH);
if ((wbTemp >= 79) && (wbTemp < 82))
{
tempSelection80(flowRate, wetBulbTemp, roundedCoolingTons, approach, range);
}
else if ((wbTemp < 79 ) && (wbTemp >= 77))
{
tempSelection78(flowRate, wetBulbTemp, roundedCoolingTons, approach, range);
}
else if ((wbTemp < 77) && (wbTemp >= 75))
{
tempSelection76(flowRate, wetBulbTemp, roundedCoolingTons, approach, range);
}
else if ((wbTemp < 75) && (wbTemp >= 73))
{
tempSelection74(flowRate, wetBulbTemp, roundedCoolingTons, approach, range);
}
else if ((wbTemp < 73) && (wbTemp >= 71))
{
tempSelection72(flowRate, wetBulbTemp, roundedCoolingTons, approach, range);
}
else if ((wbTemp < 71) && (wbTemp >= 69))
{
tempSelection70(flowRate, wetBulbTemp, roundedCoolingTons, approach, range);
}
else if ((wbTemp < 69) && (wbTemp >= 67))
{
tempSelection68(flowRate, wetBulbTemp, roundedCoolingTons, approach, range);
}
else
{
tableButton = new JButton("Cooling Tower Cannot Handle Temperatures In This Wet Bulb");
}
tableButton.setRolloverEnabled(false);
add(nextButton, BorderLayout.EAST);
add(prevButton, BorderLayout.WEST);
add(tableButton, BorderLayout.CENTER);
}
private class ButtonListener implements ActionListener
{
@Override
public void actionPerformed(ActionEvent e)
{
if (e.getSource() == goBackButton)
{
dispose();
}
else if (e.getSource() == exitButton)
{
System.exit(0);
}
else if (e.getSource() == nextButton)
{
String t = tableButton.getText();
tableButton.updateUI();
String s = ((ImageIcon)tableButton.getIcon()).toString();
if ((wbTemp >= 79) && (wbTemp < 82))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor80[i]))
{
if (i == 6)
{
count = 0;
}
else
{
count = (i+1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor80[count], tablesFor80[count]));
}
else if ((wbTemp < 79 ) && (wbTemp >= 77))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor78[i]))
{
if (i == 6)
{
count = 0;
}
else
{
count = (i+1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor78[count], tablesFor78[count]));
}
else if ((wbTemp < 77) && (wbTemp >= 75))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor76[i]))
{
if (i == 6)
{
count = 0;
}
else
{
count = (i+1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor76[count], tablesFor76[count]));
}
else if ((wbTemp < 75) && (wbTemp >= 73))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor74[i]))
{
if (i == 6)
{
count = 0;
}
else
{
count = (i+1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor74[count], tablesFor74[count]));
}
else if ((wbTemp < 73) && (wbTemp >= 71))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor72[i]))
{
if (i == 6)
{
count = 0;
}
else
{
count = (i+1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor72[count], tablesFor72[count]));
}
else if ((wbTemp < 71) && (wbTemp >= 69))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor70[i]))
{
if (i == 6)
{
count = 0;
}
else
{
count = (i+1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor70[count], tablesFor70[count]));
}
else if ((wbTemp < 69) && (wbTemp >= 67))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor68[i]))
{
if (i == 6)
{
count = 0;
}
else
{
count = (i+1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor68[count], tablesFor68[count]));
}
tableButton.setRolloverEnabled(false);
add(tableButton, BorderLayout.CENTER);
}
else if (e.getSource() == prevButton)
{
String t = tableButton.getText();
tableButton.updateUI();
String s = ((ImageIcon)tableButton.getIcon()).toString();
if ((wbTemp >= 79) && (wbTemp < 82))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor80[i]))
{
if (i == 0)
{
count = 6;
}
else
{
count = (i-1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor80[count], tablesFor80[count]));
}
else if ((wbTemp < 79 ) && (wbTemp >= 77))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor78[i]))
{
if (i == 0)
{
count = 6;
}
else
{
count = (i-1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor78[count], tablesFor78[count]));
}
else if ((wbTemp < 77) && (wbTemp >= 75))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor76[i]))
{
if (i == 0)
{
count = 6;
}
else
{
count = (i-1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor76[count], tablesFor76[count]));
}
else if ((wbTemp < 75) && (wbTemp >= 73))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor74[i]))
{
if (i == 0)
{
count = 6;
}
else
{
count = (i-1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor74[count], tablesFor74[count]));
}
else if ((wbTemp < 73) && (wbTemp >= 71))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor72[i]))
{
if (i == 0)
{
count = 6;
}
else
{
count = (i-1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor72[count], tablesFor72[count]));
}
else if ((wbTemp < 71) && (wbTemp >= 69))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor70[i]))
{
if (i == 0)
{
count = 6;
}
else
{
count = (i-1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor70[count], tablesFor70[count]));
}
else if ((wbTemp < 69) && (wbTemp >= 67))
{
if (t.equals("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables."))
{
count = 0;
}
else
{
for (int i = 0; i <= 6; i++)
{
if (s.equals(tablesFor68[i]))
{
if (i == 0)
{
count = 6;
}
else
{
count = (i-1);
}
}
}
}
tableButton = new JButton(new ImageIcon(tablesFor68[count], tablesFor68[count]));
}
tableButton.setRolloverEnabled(false);
add(tableButton, BorderLayout.CENTER);
}
}
}
else
{
tableButton = new JButton("Cannot Find Model for Variables Given. Adjust or Scroll to Look Through Tables.");
}
}
if(condition1) {
//(Block 1)
} else if(condition2) {
//(Block 2)
} else {
//(Block 3)
}