效果图:

代码实现:
import javax.swing.*;
import java.awt.*;
//计算器界面
public class demo extends JFrame {
public demo02(){
super("计算器");
this.setBounds(700,250,230,230);
JPanel vp = new JPanel();//输入框面板
JTextField textField = new JTextField();//输入框
textField.setText("0.");
textField.setColumns(18);
textField.setEditable(false);//禁止编辑
textField.setHorizontalAlignment(SwingConstants.RIGHT);//文本框内容局右侧显示
vp.add(textField);
this.add(vp, BorderLayout.NORTH);//将输入框放在北部
JPanel cbp = new JPanel();//清楚按钮面板
this.add(cbp,BorderLayout.CENTER);//中间显示
String[] str = {"CE","C","BackSpace"};
JButton but[] = new JButton[str.length];
for(int i = 0; i < str.length; i++){
but[i] = new JButton(str[i]);
cbp.add(but[i]);
}
JPanel bp = new JPanel();//输入按钮面板
bp.setLayout(new GridLayout(4,4,5,5));//网格布局,4行4列,水平垂直间距为5
this.add(bp,BorderLayout.SOUTH);//放在南部
String[][] str1 = {{"1","2","3","+"},{"4","5","6","-"},{"7","8","9","*"},{".","0","=","/"}};
JButton[] but1 = new JButton[16];
for(int i = 0; i < str1.length; i++){
for(int j = 0; j < str1.length; j++){
String str3 = str1[i][j];//存储字符串
but1[i*4+j] = new JButton(str3);//创建按钮
bp.add(but1[i*4+j]);//将按钮添加到面板中
}
}
this.setVisible(true);
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
public static void main(String[] args) {
new demo();
}
}