动手动脑(2)

//方法重载
public class MethodOverload {

    public static void main(String[] args) {
        System.out.println("The square of integer 7 is " + square(7));
        System.out.println("\nThe square of double 7.5 is " + square(7.5));
    }

    public static int square(int x) {
        return x * x;
    }

    public static double square(double y) {
        return y * y;
    }
}

运行结果：

以上代码为Java中方法的重载,构成条件为:

1.方法名相同

2.参数类型、个数或参数类型的顺序不同，与返回值类型无关

在Java中定义方法

//求平方数的静方法
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;
    }
}

运行结果:

随机数生成

使用Math.random()生成随机数

// RandomInt.java
// Shifted, scaled random integers
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 );     //生成0~5之间的随机数
         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 );
   }
}

 运行结果:

使用Random类生成随机数

import java.util.*;

public class TestRandom
{
    public static void main(String[] args) 
    {
        Random rand = new Random();
        System.out.println("rand.nextBoolean()：" + rand.nextBoolean());
        byte[] buffer = new byte[16];
        rand.nextBytes(buffer);
        System.out.println(Arrays.toString(buffer));
        //生成0.0~1.0之间的伪随机double数
        System.out.println("rand.nextDouble()：" + rand.nextDouble());
        //生成0.0~1.0之间的伪随机float数
        System.out.println("rand.nextFloat()：" + rand.nextFloat());
        //生成平均值是 0.0，标准差是 1.0的伪高斯数
        System.out.println("rand.nextGaussian()：" + rand.nextGaussian());
        //生成一个处于long整数取值范围的伪随机整数
        System.out.println("rand.nextInt()：" + rand.nextInt());
        //生成0~26之间的伪随机整数
        System.out.println("rand.nextInt(26)：" + rand.nextInt(26));
        //生成一个处于long整数取值范围的伪随机整数
        System.out.println("rand.nextLong()：" +  rand.nextLong());
    }
}
   

 运行结果:

利用种子生成随机数

import java.util.Random;
/*
 * 随机数是种子经过计算生成的。

    不含参的构造函数每次都使用当前时间作为种子，随机性更强
    而含参的构造函数其实是伪随机，更有可预见性

 */
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()); 
    }
}

运行结果: