练习一：四则运算

import java.util.*;
public class 四则运算 {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		int a,b;
		Scanner sc = new Scanner(System.in);
		//int Max=4;
		//int min=1;
		//Random random=new Random();
		//int s=random.nextInt(Max)%(Max-min+1)+min;
		System.out.println("请输入你的题量；");
		int c=sc.nextInt();
		for(int i=0;i<c;i++)
		{
		int s=1+(int)(Math.random()*4);
		switch(s)
		{
		case 1:
				int k;
				a=1+(int)(Math.random()*100);
				b=1+(int)(Math.random()*100);
				System.out.println(a+"+"+ b + "=");
				k=sc.nextInt();
				if(k==a+b)
					System.out.println("答案正确；");
				else System.out.println("答案错误,正确答案为"+(a+b));	
				break;
		case 2:
			int l=0;
			a=1+(int)(Math.random()*100);
			b=1+(int)(Math.random()*100);
			System.out.println(a+"-"+ b + "=");
			l=sc.nextInt();
			if(l==a-b)
			{
				System.out.println("答案正确；");
				if(a<b)
					System.out.println("改答案为负数；");
			}
			else System.out.println("答案错误,正确答案为"+(a-b));	
			break;
		case 3:
			int m;
			a=1+(int)(Math.random()*10);
			b=1+(int)(Math.random()*10);
			System.out.println(a+"*"+ b + "=");
			m=sc.nextInt();
			if(m==a*b)
				System.out.println("答案正确；");
			else System.out.println("答案错误,正确答案为"+(a*b));	
			break;
		case 4:
				int n;
				a=1+(int)(Math.random()*30);
				b=1+(int)(Math.random()*30);
				System.out.println(a+"/"+ b + "=");
				n=sc.nextInt();
				if(n==a/b)
					System.out.println("答案正确；");
				else System.out.println("答案错误,正确答案为"+(a/b));	
				break;
			}
		}
	}
}