新手求教一个 java 四则运算小程序...

java源文件如下 Calc.java：
import javax.swing.JApplet;
import javax.swing.JTextArea;

public class Calc extends JApplet {

public void init() {
double first = Double.parseDouble(getParameter("first"));
double second = Double.parseDouble(getParameter("second"));
char operator = getParameter("operator").charAt(0);
double result = 0;

switch(operator) {
case '+': result = first + second; break;
case '-': result = first - second; break;
case '*': result = first * second; break;
case '/': result = first / second; break;
}

JTextArea text = new JTextArea(3,100);
text.setEditable(false);
String a = "************************";
String s = String.format("%.2f %c %.2f = %.2f",first,operator,second,result);
text.append(a+"\n");
text.append(s+"\n");
text.append(a+"\n");
add(text);
}

}

html文件如下 a.html：









将java文件编译后得到的Calc.class文件与html文件放在同一个目录下，然后用浏览器打开那个html文件就能看到了。当然你的浏览器得支持java才行。

普通的java代码如下 Calc.java
public class Calc extends JApplet {

public static void main(String[] args) {
double first = 1.2;
double second = 2.4;
char operator = '+';
double result = 0;

switch(operator) {
case '+': result = first + second; break;
case '-': result = first - second; break;
case '*': result = first * second; break;
case '/': result = first / second; break;
}
String a = "************************";
String s = String.format("%.2f %c %.2f = %.2f",first,operator,second,result);

System.out.println(a);
System.out.println(s);
System.out.println(a);
}

}