四则运算 第二次

import javax.swing.JButton;
import java.awt.Graphics;
import java.awt.FlowLayout;
import javax.swing.JFrame;
import javax.swing.JTextField;
import java.awt.Color;
import java.awt.Container;
import java.awt.Dimension;
import javax.swing.JPanel;
import java.awt.Font;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
public class computer extends JFrame {
computer() {
super("简易计算器");
Font f = new Font("黑体", 30, 30);
JTextField jt1 = new JTextField(null);
JTextField jt2 = new JTextField(null);
jt1.setFont(f);
jt2.setFont(f);
jt1.setHorizontalAlignment(JTextField.RIGHT);
jt2.setHorizontalAlignment(JTextField.RIGHT);
Container c = getContentPane();
c.setLayout(new FlowLayout(FlowLayout.LEFT, 5, 5));
c.add(jt1);
c.add(jt2);
jt1.setPreferredSize(new Dimension(370, 70));
jt2.setPreferredSize(new Dimension(370, 75));
jt1.setEditable(false);
jt2.setEditable(false);
JButton jb[] = new JButton[16];
for (int j = 0; j < 16; j++) {
jb[j] = new JButton();
jb[j].setBackground(Color.WHITE);
jb[j].setFocusable(false);
jb[j].setPreferredSize(new Dimension(90, 90));
jb[j].setFont(f);
c.add(jb[j]);
}
this.setResizable(false);
//对各个按钮的名称赋值
jb[0].setText("+");
jb[1].setText("-");
jb[2].setText("*");
jb[3].setText("/");
jb[4].setText("1");
jb[5].setText("2");
jb[6].setText("3");
jb[7].setText("C");
jb[7].setBackground(Color.ORANGE);
jb[8].setText("4");
jb[9].setText("5");
jb[10].setText("6");
jb[11].setText("0");
jb[12].setText("7");
jb[13].setText("8");
jb[14].setText("9");
jb[15].setText("=");

JButton Button_num[] = {
jb[4],
jb[5],
jb[6],
jb[8],
jb[9],
jb[10],
jb[11],
jb[12],
jb[13],
jb[14]
};
for (int i = 0; i < Button_num.length; i++) {
Button_num[i].addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
JButton action_Button = (JButton) e.getSource();
jt2.setText(jt2.getText() + action_Button.getText());
}
});
}
for (int j = 0; j < 4; j++) {
jb[j].addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
String s = jt2.getText();
char ch = s.charAt(s.length() - 1);

if (ch == '+' || ch == '-' || ch == '*' || ch == '/')((JButton) e.getSource()).setEnabled(false);
else {
jt1.setText(jt2.getText());
jt2.setText(((JButton) e.getSource()).getText());
}

}
});
}
jb[7].addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
jt1.setText(null);
jt2.setText(null);
}
}

);
jb[15].addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
try {
String Calculate_String = jt1.getText() + jt2.getText();
int result = calculation.result(Calculate_String);
jt1.setText(null);
jt2.setText(Integer.toString(result));
} catch(ArithmeticException ex) {
jt1.setText(null);
jt2.setText("ERROR");
}
}
});
}
public static void main(String args[]) {
computer app = new computer();
app.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
app.setSize(400, 580);
app.setVisible(true);
}
}

//再定义一个计算类calculation.java:
public class calculation {
calculation() {};
boolean is_operator(char ch) {
if (ch == '+' || ch == '-' || ch == '*' || ch == '/') return true;
else return false;
}
static int result(String s) {
String ch[] = {
"+",
"-",
"*",
"/"
};
int i = 0;
int index;
while (s.indexOf(ch[i]) == -1 && i < 4) {
i++;
}
if (i == 4) return - 1;
else index = s.indexOf(ch[i]);
String s1 = s.substring(0, index);
String s2 = s.substring(index + 1, s.length());
if (i == 0) return Integer.parseInt(s1) + Integer.parseInt(s2);
if (i == 1) return Integer.parseInt(s1) - Integer.parseInt(s2);
if (i == 2) return Integer.parseInt(s1) * Integer.parseInt(s2);
if (i == 3 && Integer.parseInt(s2) != 0) return Integer.parseInt(s1) / Integer.parseInt(s2);
else if (i == 3 && Integer.parseInt(s2) == 0) {
throw new ArithmeticException();
}
return - 1;
}

}