//解答：
public static void main(String[] args) {
		/*
 		 * 让用户输入a,b,c
		 * 计算delta
		 * <0 =0 >0三种情况
		 * /
 		Scanner scanner=new Scanner(System.in);
		System.out.println("enter a,b,c");
		double a=scanner.nextDouble();
		double b=scanner.nextDouble();
		double c=scanner.nextDouble();
		double del=b*b-(4*a*c);
		double r1,r2;
		if(del==0) {
			r1=r2=(-b+Math.pow(Math.pow(b,2)-(4*a*c),0.5))/(2*a);
			System.out.println("r1=r2="+r1);
		}else if(del>0) {
			r1=(-b+Math.pow(Math.pow(b,2)-(4*a*c),0.5))/(2*a);
			r2=(-b-Math.pow(Math.pow(b,2)-(4*a*c),0.5))/(2*a);
			System.out.println("r1="+r1+" r2="+r2);
		}else {
			System.out.println(" the question has no real roots");
		}
}

//解答：
public static void main(String[] args) {
	/*
	 * 首先三位数分别为个位，十位，百位，输入一个三位数
	 * 将个位，十位，百位对应的数字取出来
	 * 判断各位和百位的数字是否一样
	 * 	一样就是回文数字，反之则不是 
	 */
	Scanner scanner =new Scanner(System.in);
	System.out.println("please enter a number");
	int n=scanner.nextInt();
	int a=n%10;
	int b=n/100;
	if(a==b) {
		System.out.println(n+"is a palindrome");
	}else {
		System.out.println(n+"is not a palindrome");
	}	
}

public static void main(String[] args) {
	Scanner scanner=new Scanner(System.in);
	/*
	 * 电脑随机产生0-2分别代表石头，剪刀，布
	 * 用户输入0-2也代表石头剪刀布
	 * 当电脑的随机数+1并对3取余后等于用户输入的值，电脑赢
	 * 直接相等平局，
	 * 否则用户赢
	 * */
	int com=(int)Math.random()*3;
	System.out.println("please a number");
	int user=scanner.nextInt();
	String coms="";
	String users="";
	if(com==0){
		coms="scissor";
	}else if(com==1){
		coms="rock";
	}else{
		coms="paper";
	}
	if(user==0){
		users="scissor";
	}else if(user==1){
		users="rock";
	}else{
		users="paper";
	}
	if(com==user){
		System.out.printf("The computer is %s.You are %s.It is a draw",coms,users);
	}else if((com+1)%3==user){
		System.out.printf("The computer is %s.You are %s.You win",coms,users);
	}else{
		System.out.printf("The computer is %s.You are %s.You lose",coms,users);
	}
}