简单的计算器程序，可以使用按钮+键盘两种方式输入

import java.awt.Color; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.awt.event.KeyEvent; import java.awt.event.KeyListener; import java.awt.event.WindowAdapter; import java.awt.event.WindowEvent; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JMenu; import javax.swing.JMenuBar; import javax.swing.JMenuItem; import javax.swing.JTextField; import javax.swing.SwingConstants; @SuppressWarnings("serial") public class cal extends JFrame implements ActionListener,KeyListener { JButton bt1=new JButton("1"); JButton bt2=new JButton("2"); JButton bt3=new JButton("3"); JButton bt4=new JButton("4"); JButton bt5=new JButton("5"); JButton bt6=new JButton("6"); JButton bt7=new JButton("7"); JButton bt8=new JButton("8"); JButton bt9=new JButton("9"); JButton bt10=new JButton("0"); JButton point=new JButton("."); JButton jia=new JButton("+"); JButton jian=new JButton("-"); JButton cheng=new JButton("×"); JButton chu=new JButton("÷"); JButton deng=new JButton("="); JTextField tf=new JTextField(); JMenuBar mub; JMenu mu1,mu2,mu3; JMenuItem itm1,itm2,itm3,itm4,itm5,itm6,itm7; String total="0"; String mer; //记忆 double a,b,c; double one=1.0; cal() { super("计算器"); setLocationRelativeTo(null); setLayout(null); setVisible(true); setResizable(false); setSize(215,297); setBackground(Color.green); mub=new JMenuBar(); setJMenuBar(mub); add(bt10); bt10.setBounds(5,200,46,35); bt10.setFocusPainted(false); add(point); point.setBounds(56, 200, 46, 35); point.setFocusPainted(false); add(bt1); bt1.setBounds(5, 160, 46, 35); bt1.setFocusPainted(false); add(bt2); bt2.setBounds(56, 160, 46, 35); bt2.setFocusPainted(false); add(bt3); bt3.setBounds(105, 160, 46, 35); bt3.setFocusPainted(false); add(bt4); bt4.setBounds(5, 120, 46, 35); bt4.setFocusPainted(false); add(bt5); bt5.setBounds(56, 120, 46, 35); bt5.setFocusPainted(false); add(bt6); bt6.setBounds(105, 120, 46, 35); bt6.setFocusPainted(false); add(bt7); bt7.setBounds(5, 80, 46,35); bt7.setFocusPainted(false); add(bt8); bt8.setBounds(56,80, 46, 35); bt8.setFocusPainted(false); add(bt9); bt9.setBounds(105, 80, 46, 35); bt9.setFocusPainted(false); add(jia); jia.setBounds(105, 200, 46, 35); jia.setFocusPainted(false); jian.setFocusPainted(false); cheng.setFocusPainted(false); chu.setFocusPainted(false); deng.setFocusPainted(false); add(deng); deng.setBounds(156, 200, 46, 35); add(jian); jian.setBounds(156, 80, 46, 35); add(cheng); cheng.setBounds(156, 120, 46, 35); add(chu); chu.setBounds(156, 160, 46, 35); add(tf); tf.setBounds(5, 0, 200, 70); tf.setHorizontalAlignment(SwingConstants.RIGHT); tf.setEditable(false); tf.setText("0"); //菜单栏 mu1=new JMenu("文件"); mu3=new JMenu("编辑"); mu2=new JMenu("帮助"); itm3=new JMenuItem("清除(C)"); itm4=new JMenuItem("复制"); itm5=new JMenuItem("粘贴"); itm6=new JMenuItem("←(B)"); itm1=new JMenuItem("退出"); itm2=new JMenuItem("关于"); itm7=new JMenuItem("科学型"); mub.add(mu1); mub.add(mu3); mub.add(mu2); mub.add(itm3); mub.add(itm6); mu3.add(itm4); mu3.add(itm5); //mu1.add(itm7); mu1.add(itm1); mu2.add(itm2); tf.grabFocus(); //监听器 itm1.addActionListener(this); itm2.addActionListener(this); itm3.addActionListener(this); itm4.addActionListener(this); itm5.addActionListener(this); itm6.addActionListener(this); itm7.addActionListener(this); bt1.addActionListener(this); bt2.addActionListener(this); bt3.addActionListener(this); bt4.addActionListener(this); bt5.addActionListener(this); bt6.addActionListener(this); bt7.addActionListener(this); bt8.addActionListener(this); bt9.addActionListener(this); bt10.addActionListener(this); point.addActionListener(this); jia.addActionListener(this); jian.addActionListener(this); cheng.addActionListener(this); chu.addActionListener(this); deng.addActionListener(this); tf.addKeyListener(this); addWindowListener(new WindowAdapter(){ public void windowClosing(WindowEvent e){System.exit(0);}}); } public static void main(String args[]) { cal ca=new cal(); ca.show(); } public void answer(String str) { String [] a=str.split("\\+|\\-|×|÷"); if(a.length==1) {} else { double first=Double.parseDouble(a[0]); double second=Double.parseDouble(a[1]); String [] b=str.split("0|1|2|3|4|5|6|7|8|9|\\."); String c=b[a[0].length()]; //C是运算符 char[] d=c.toCharArray(); if(d[0]=='+') { double add=first+second; if(add%one==0.0) { int result=(int)add; str=String.valueOf(result); tf.setText(str); total=str; } else { str=String.valueOf(add); tf.setText(str); total=str; } } else if(d[0]=='-') { double jianfa=first-second; if(jianfa%one==0.0) { int result=(int)jianfa; str=String.valueOf(result); tf.setText(str); total=str; } else { str=String.valueOf(jianfa); tf.setText(str); total=str; } } else if(d[0]=='×') { double chengfa=first*second; if(chengfa%one==0.0) { int result=(int)chengfa; str=String.valueOf(result); tf.setText(str); total=str; } else { str=String.valueOf(chengfa); tf.setText(str); total=str; } } else if(d[0]=='÷') { if(second==0) {} else { double chufa=first/second; if(chufa%one==0.0) { int result=(int)chufa; str=String.valueOf(result); tf.setText(str); total=str; } else { str=String.valueOf(chufa); tf.setText(str); total=str; } } } } } @Override public void actionPerformed(ActionEvent e) { // TODO Auto-generated method stub tf.grabFocus(); if (e.getSource()==itm1) { System.exit(0); } else if(e.getSource()==itm2) { about ab=new about(); ab.show(); this.hide(); //JOptionPane.showMessageDialog(null, "\t\tJava 计算器\n\n \t\t编写:赵远", "计算器", JOptionPane.ERROR_MESSAGE); } else if(e.getSource()==bt1) { String []b=total.split("\\+|\\-|×|÷"); if(b.length==1) { if(total=="0") { total="1";tf.setText(total); } else { total+="1";tf.setText(total); } } else { char zero01=total.charAt(total.length()-1); char zero02=total.charAt(total.length()-2); if(zero01=='0'&&(zero02=='+'||zero02=='-'||zero02=='×'||zero02=='÷')) { String Backspace=""; for(int i=0;i<total.length()-1;i++) { char a=total.charAt(i); Backspace+=String.valueOf(a); } total=Backspace; total+="1";tf.setText(total); } else { total+="1";tf.setText(total); } } } else if(e.getSource()==bt2) { String []b=total.split("\\+|\\-|×|÷"); if(b.length==1) { if(total=="0") { total="2";tf.setText(total); } else { total+="2";tf.setText(total); } } else { char zero01=total.charAt(total.length()-1); char zero02=total.charAt(total.length()-2); if(zero01=='0'&&(zero02=='+'||zero02=='-'||zero02=='×'||zero02=='÷')) { String Backspace=""; for(int i=0;i<total.length()-1;i++) { char a=total.charAt(i); Backspace+=String.valueOf(a); } total=Backspace; total+="2";tf.setText(total); } else { total+="2";tf.setText(total); } } } else