动手动脑

一个求平方数的静方法Square。

public class SquareInt {

	public static void main(String[] args) {
		int result;

		for (int x = 1; x <= 10; x++) {
			result = square(x);
			// Math库中也提供了求平方数的方法
			// result=(int)Math.pow(x,2);
			System.out.println("The square of " + x + " is " + result + "\n");
		}
	}

	// 自定义求平方数的静态方法
	public static int square(int y) {
		return y * y;
	}
}

随机数的生成方法。20 Random Numbers from 1 to 6"

import javax.swing.JOptionPane;

public class RandomInt {
   public static void main( String args[] )
   {
      int value;
      String output = "";

      for ( int i = 1; i <= 20; i++ ) {
         value = 1 + (int) ( Math.random() * 6 );
         output += value + "  ";
         
         if ( i % 5 == 0 )
            output += "\n";
      }

      JOptionPane.showMessageDialog( null, output,
         "20 Random Numbers from 1 to 6",
         JOptionPane.INFORMATION_MESSAGE );

      System.exit( 0 );
   }
}

相同“种子（seed）”的Random对象会生成相同的随机数。

import java.util.Random;

public class TestSeed
{
    public static void main(String[] args)
	{
        Random r1 = new Random(50);
        System.out.println("第一个种子为50的Random对象");
        System.out.println("r1.nextBoolean():\t" + r1.nextBoolean());
        System.out.println("r1.nextInt():\t\t" + r1.nextInt());
        System.out.println("r1.nextDouble():\t" + r1.nextDouble());
        System.out.println("r1.nextGaussian():\t" + r1.nextGaussian());
        System.out.println("---------------------------");
        
        Random r2 = new Random(50);
        System.out.println("第二个种子为50的Random对象");
        System.out.println("r2.nextBoolean():\t" + r2.nextBoolean());
        System.out.println("r2.nextInt():\t\t" + r2.nextInt());
        System.out.println("r2.nextDouble():\t" + r2.nextDouble());
        System.out.println("r2.nextGaussian():\t" + r2.nextGaussian());
        System.out.println("---------------------------");
        
        Random r3 = new Random(100);
        System.out.println("种子为100的Random对象");
        System.out.println("r3.nextBoolean():\t" + r3.nextBoolean());
        System.out.println("r3.nextInt():\t\t" + r3.nextInt());
        System.out.println("r3.nextDouble():\t" + r3.nextDouble());
        System.out.println("r3.nextGaussian():\t" + r3.nextGaussian());
        
       
        Random r4 = new Random(System.currentTimeMillis());
        System.out.println("以当前时间为种子的Random对象");
        System.out.println("r3.nextBoolean():\t" + r4.nextBoolean());
        System.out.println("r3.nextInt():\t\t" + r4.nextInt());
        System.out.println("r3.nextDouble():\t" + r4.nextDouble());
        System.out.println("r3.nextGaussian():\t" + r4.nextGaussian()); 
    }
}

编写一个方法，使用以上算法生成指定数目（比如1000个）的随机整数。

package Temp;

public class GetRandom {
    public static void main(String[] args) {

        int Modulus= (int) (Math.pow(2,31)-1);
        int Multiplier=16807;
        int c=0;
        long x=1;
        for (int i = 0; i < 1000; i++) {
            x=(Multiplier*x+c)%Modulus;
            System.out.println(x);
        }
    }
}