在java中只接受一位数字
我正在写一个简单的程序,它接受多个输入,然后显示最大值和第二大值。我唯一的问题是我希望程序只接受个位数。我知道这是最基本的,但请容忍我。到目前为止,我编写的代码是:在java中只接受一位数字,java,Java,我正在写一个简单的程序,它接受多个输入,然后显示最大值和第二大值。我唯一的问题是我希望程序只接受个位数。我知道这是最基本的,但请容忍我。到目前为止,我编写的代码是: import javax.swing.JOptionPane; public class Largest { public static void main (String args[]) { /*Set variables and include a while function to for
import javax.swing.JOptionPane;
public class Largest
{
public static void main (String args[])
{
/*Set variables and include a while function to force the program to take
* ten numbers before proceeding to the rest of the program. */
int counter = 0;
int number = 0;
int largest = 0;
int second = 0;
while (counter < 10)
{
// Set the counter
counter++;
//Input integer, set the largest number as the first output
number = Integer.parseInt(JOptionPane.showInputDialog("Enter integer"));
if (number >= largest) {
largest=number;
} else if (number >= second && number <= largest) {
// Set the second largest integer as the output
second=number;
}
}
//Display the largest number, followed by the second largest number
System.out.println("Largest number input: " + largest);
System.out.println("Second largest input: " + second);
System.exit(0); //terminate the application
} //end method main
} //end class
import javax.swing.JOptionPane;
公务舱
{
公共静态void main(字符串参数[])
{
/*设置变量并包含while函数以强制程序执行
*在继续程序的其余部分之前,请输入10个数字*/
int计数器=0;
整数=0;
int最大=0;
int秒=0;
while(计数器<10)
{
//设置计数器
计数器++;
//输入整数,设置最大的数字作为第一个输出
number=Integer.parseInt(JOptionPane.showInputDialog(“输入整数”);
如果(数量>=最大){
最大=数量;
}else if(number>=second&&number//设置计数器
计数器++;
while(true){
//输入整数,设置最大的数字作为第一个输出
number=Integer.parseInt(JOptionPane.showInputDialog(“输入整数”);
if(number<10&&number>-10)break;//如果是一位数字,则可以
JOptionPane.showMessageDialog(空,“仅输入一位数字”,
“数字太多”,JOptionPane。错误消息);
}
这样做的目的是启动一个无限循环。如果数字只有一个数字,它将结束循环并继续。否则,它将再次从循环的开头开始,并要求输入一个有效的数字。只需使用一个自定义JOptionDialog,将JTextField限制为1个字符宽度。对于这种类型的问题,我个人会使用
它允许您限制进入字段的字符类型以及字符数
public class RestrictInput {
public static void main(String[] args) {
new RestrictInput();
}
public RestrictInput() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
JTextField field = new JTextField(2);
field.setHorizontalAlignment(JTextField.RIGHT);
((AbstractDocument) field.getDocument()).setDocumentFilter(new RestrictFilter());
JPanel panel = new JPanel(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
panel.add(new JLabel("Please enter a integer:"), gbc);
gbc.gridx++;
gbc.anchor = GridBagConstraints.WEST;
gbc.weightx = 1;
panel.add(field, gbc);
int result = JOptionPane.showConfirmDialog(null, panel, "Input", JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE);
if (result == JOptionPane.OK_OPTION) {
System.out.println("Use entered " + field.getText());
}
}
});
}
public class RestrictFilter extends DocumentFilter {
public void insertString(DocumentFilter.FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
String currentText = fb.getDocument().getText(0, fb.getDocument().getLength());
if (currentText.startsWith("-") || text.equals("-") || fb.getDocument().getLength() < 1) {
String value = text.substring(0, 1);
if (value.equals("-")) {
if (currentText.startsWith("-")) {
super.remove(fb, 0, 1);
} else {
super.insertString(fb, 0, value, attr);
}
} else if (fb.getDocument().getLength() < 2 && (value.equals("-") || Character.isDigit(value.charAt(0)))) {
super.insertString(fb, offset, value, attr);
}
}
}
public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String string, AttributeSet attr) throws BadLocationException {
if (length > 0) {
fb.remove(offset, length);
}
insertString(fb, offset, string, attr);
}
}
}
公共类限制输入{
公共静态void main(字符串[]args){
新的限制输入();
}
公共限制输入(){
invokeLater(新的Runnable(){
@凌驾
公开募捐{
试一试{
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
}捕获(ClassNotFoundException ex){
}catch(实例化异常){
}捕获(非法访问例外){
}捕获(无支持的LookandFeelexception ex){
}
JTextField=新的JTextField(2);
field.setHorizontalAlignment(JTextField.RIGHT);
((AbstractDocument)field.getDocument()).setDocumentFilter(新的RestrictFilter());
JPanel panel=newjpanel(newgridbagloayout());
GridBagConstraints gbc=新的GridBagConstraints();
gbc.gridx=0;
gbc.gridy=0;
panel.add(新的JLabel(“请输入一个整数”)、gbc;
gbc.gridx++;
gbc.anchor=GridBagConstraints.WEST;
gbc.weightx=1;
面板。添加(字段,gbc);
int result=JOptionPane.showConfirmDialog(null,面板,“输入”,JOptionPane.OK\u取消选项,JOptionPane.QUESTION\u消息);
if(result==JOptionPane.OK\u选项){
System.out.println(“使用entered”+field.getText());
}
}
});
}
公共类RestrictFilter扩展了DocumentFilter{
public void insertString(DocumentFilter.FilterBypass fb,int offset,String text,AttributeSet attr)引发BadLocationException{
字符串currentText=fb.getDocument().getText(0,fb.getDocument().getLength());
if(currentText.startsWith(“-”)| | text.equals(“-”| | fb.getDocument().getLength()<1){
字符串值=文本。子字符串(0,1);
if(值等于(“-”){
if(currentText.startsWith(“-”){
超级。移除(fb,0,1);
}否则{
super.insertString(fb,0,value,attr);
}
}else if(fb.getDocument().getLength()<2&(value.equals(“-”)| | Character.isDigit(value.charAt(0))){
super.insertString(fb,offset,value,attr);
}
}
}
public void replace(DocumentFilter.FilterBypass fb,int offset,int length,String String,AttributeSet attr)引发BadLocationException{
如果(长度>0){
fb.移除(偏移、长度);
}
插入字符串(fb、偏移量、字符串、属性);
}
}
}
签出,特别是实现文档过滤器的部分您的意思是只希望他们能够实际输入一个数字(比如它不允许您输入两个字符),还是它应该只接受一个数字(比如如果超过9就会抛出错误)?刚刚意识到,如果输入,程序将始终显示第二高的数字为0。不确定为什么…它不应在任何输入中允许两位数。回到VB,我记得将变量设置为仅允许一位数,我相信,但这太长了ago@user1798926看看我的答案。你应该再问一次是否无效你也应该检查number>=0
,或者用户可以输入几个数字的负值。谢谢,这与我刚才尝试的非常接近。我仍然有一个问题,就是总是出现零,我想我必须限制用户输入零谢谢你的链接,我还没有使用limiters@MadPr这就是我的意思-我确信JTextField有一个“显示宽度”和一个“最大输入长度”,但后来我意识到我把它和HTML表单混淆了!你的答案肯定更完整,并且强制使用数字字符。
public class RestrictInput {
public static void main(String[] args) {
new RestrictInput();
}
public RestrictInput() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException ex) {
} catch (InstantiationException ex) {
} catch (IllegalAccessException ex) {
} catch (UnsupportedLookAndFeelException ex) {
}
JTextField field = new JTextField(2);
field.setHorizontalAlignment(JTextField.RIGHT);
((AbstractDocument) field.getDocument()).setDocumentFilter(new RestrictFilter());
JPanel panel = new JPanel(new GridBagLayout());
GridBagConstraints gbc = new GridBagConstraints();
gbc.gridx = 0;
gbc.gridy = 0;
panel.add(new JLabel("Please enter a integer:"), gbc);
gbc.gridx++;
gbc.anchor = GridBagConstraints.WEST;
gbc.weightx = 1;
panel.add(field, gbc);
int result = JOptionPane.showConfirmDialog(null, panel, "Input", JOptionPane.OK_CANCEL_OPTION, JOptionPane.QUESTION_MESSAGE);
if (result == JOptionPane.OK_OPTION) {
System.out.println("Use entered " + field.getText());
}
}
});
}
public class RestrictFilter extends DocumentFilter {
public void insertString(DocumentFilter.FilterBypass fb, int offset, String text, AttributeSet attr) throws BadLocationException {
String currentText = fb.getDocument().getText(0, fb.getDocument().getLength());
if (currentText.startsWith("-") || text.equals("-") || fb.getDocument().getLength() < 1) {
String value = text.substring(0, 1);
if (value.equals("-")) {
if (currentText.startsWith("-")) {
super.remove(fb, 0, 1);
} else {
super.insertString(fb, 0, value, attr);
}
} else if (fb.getDocument().getLength() < 2 && (value.equals("-") || Character.isDigit(value.charAt(0)))) {
super.insertString(fb, offset, value, attr);
}
}
}
public void replace(DocumentFilter.FilterBypass fb, int offset, int length, String string, AttributeSet attr) throws BadLocationException {
if (length > 0) {
fb.remove(offset, length);
}
insertString(fb, offset, string, attr);
}
}
}