java中currentTimeMillis()和Math.random()

拼搏现实的明天。 2022-07-27 14:52 145阅读 0赞

在java中产生随机数  
1. currentTimeMills()  
不是int类型，需要强制转换为int，然后余10得到一位数的随机数，  
余100得到两位数的随机数。…….  
int number1 = ( int ) ( System.currentTimeMillis() %10 );  
2. Math.random()  
是double类型的数据，是小数。  
乘以10得到一位数的随机数，乘以100得到两位数的随机数。….  
int number2 = ( int ) (Math.random() \* 10 );  
**示例代码如下:**

//10以内的数做加减法
    import java.util.*;
    import javax.swing.*;
    public class Demo032302{
        public static void main( String [] args ){
            //随机产生两个随机数
            //方法之一
            //int number1 =  ( int ) ( System.currentTimeMillis() %10 );
            //int number2 = (int ) ( System.currentTimeMillis() %100 );
    
            //方法之二
            //double n = Math.random();//Math.random(); 产生的随机数是double类型小数
            //System.out.println( n );
    
            int number1 = (int) ( Math.random() * 10 );//
            int number2 = ( int ) (Math.random() * 10 );
            //System.out.println( number1 + "\t" + number2 );
    
            //threshold用于限定做加法还是做减法，如果是0做加法，如果是1做减法。
            int threshold1 = ( int ) ( Math.random() * 10 );
            int threshold = threshold1%2;
            if ( threshold == 0 )
            {
                System.out.println( "What is " + number1 + " + " + number2 + " = ? " );
                Scanner input = new Scanner( System.in );
                int answer = input.nextInt();
                if ( number1 + number2 == answer )
                    System.out.println( "you are correct!" );
                else
                    System.out.println( number1 + " + " + number2 + " = " + ( number1 + number2 ) );
            }
            else
            {
                if ( number1 < number2 ){
                    int temp = number1;
                    number1 = number2;
                    number2 = temp;
                }
                System.out.println( "What is " + number1 + " - " + number2 + " = ? " );
                Scanner input = new Scanner( System.in );
                int answer = input.nextInt();
                if ( number1 - number2 == answer )
                    System.out.println( "you are correct!" );
                else
                    System.out.println( number1 + " - " + number2 + " = " + ( number1 - number2 ) );
    
            }
    
    
    
    
        }
    }