Java计算器编程
 
import java.io.IOException;
import java.util.Scanner;
public class Jisuanqi {
	public static void main(String[] args) throws IOException {
		opreation op1 = new opreation();
		opreation op2 = new opreation();
		Scanner read = new Scanner(System.in);
		System.out.println("请输入第一个数：");
		op1.a = read.nextInt();
		System.out.println("请输入运算符：");
		char ch = (char) System.in.read();
		System.out.println("请输入第二个数：");
		op2.b = read.nextInt();		
		char c=ch;
		switch (c) {
		case '+':
			add ad = new add();
			ad.add(op1.a, op2.b);
			break;
		case '-':
			sub su = new sub();
			su.sub(op1.a, op2.b);
			break;
		case '*':
			mul mu = new mul();
			mu.mul(op1.a, op2.b);
			break;
		case '/':
			div di = new div();
			di.div(op1.a, op2.b);
			break;
		}
	}
}
class opreation{  //定义抽象操作类
	int a,b,c;
	void add(){
	}
	void sub(){
	}
	void mul(){
}
	void div(){		
}
}
class add extends opreation{//定义加法类

	 public void add(int a,int b){
		 c=a+b;
		 System.out.println(a+"+"+b+"="+c);
	 }
}
class sub extends opreation{//定义减法类

	public void sub(int a,int b){
		c=a-b;
		System.out.println(a+"-"+b+"="+c);
	}
}
class mul extends opreation{//定义乘法类
	public void mul(int a,int b){
		c=a*b;
		System.out.println(a+"*"+b+"="+c);
	}
}
class div extends opreation{//定义除法类
	public void div(int a,int b){
		if(b==0)
			System.out.println("除数不能为0");
		double c=a/b;
		System.out.println(a+"/"+b+"="+c);
	}
}