课堂作业

1.CalculateN

源代码：

import java.math.BigInteger;
import java.util.Scanner;


public class CalculateN {

    /**
     * @param args
     */
    public static void main(String[] args) {
        System.out.print("������N��");
        Scanner scanner=new Scanner(System.in);
        int number=scanner.nextInt();
        System.out.println(number+"!="+calculateN2(number));

    }

    public static long calculateN(int n) {
        if(n==1 || n==0){
            return 1;
        }

        return n*calculateN(n-1);
    }

    public static BigInteger calculateN2(int n) {
        if(n==1 || n==0){
            return BigInteger.valueOf(1);
        }
        return BigInteger.valueOf(n).multiply(calculateN2((n-1)));
    }
}

运行结果：

"C:\Program Files\Java\jdk-17\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\lib\idea_rt.jar=5401:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\郑盾\IdeaProjects\test9_15\out\production\test9_15 CalculateN

������N��

5

5!=120

Process finished with exit code 0

1. CompareFloatNumber:

源代码：

public class CompareFloatNumber {

    /**
     * @param args
     */
    public static void main(String[] args) {
        //compare();
        compare2();

    }

    private static void compare() {
        double i = 0.0001;
        double j = 0.00010000000000000001;
        System.out.println(i==j);  //�����true
    }
    private static void compare2() {
        double i = 0.0001;
        double j = 0.00010000000000000001;
        if(Math.abs(i-j)<1e-10){
            System.out.println("true");
        }
        else
        {
            System.out.println("false");
        }

    }

}

运行结果：

"C:\Program Files\Java\jdk-17\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\lib\idea_rt.jar=5629:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\郑盾\IdeaProjects\test9_15\out\production\test9_15 CompareFloatNumber

true

Process finished with exit code 0

1. MethodOverload

源代码：

// MethodOverload.java
// Using overloaded methods

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：

"C:\Program Files\Java\jdk-17\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\lib\idea_rt.jar=5715:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\郑盾\IdeaProjects\test9_15\out\production\test9_15 MethodOverload

The square of integer 7 is 49

The square of double 7.5 is 56.25

Process finished with exit code 0

1. RandomInt

源代码：

// 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 );
            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：

1. RollDie

源代码：
// RollDie.java
// Roll a six-sided die 6000 times
import javax.swing.*;

public class RollDie {
    public static void main( String args[] )
    {
        int frequency1 = 0, frequency2 = 0,
                frequency3 = 0, frequency4 = 0,
                frequency5 = 0, frequency6 = 0, face;

        // summarize results
        for ( int roll = 1; roll <= 6000; roll++ ) {
            face = 1 + (int) ( Math.random() * 6 );

            switch ( face ) {
                case 1:
                    ++frequency1;
                    break;
                case 2:
                    ++frequency2;
                    break;
                case 3:
                    ++frequency3;
                    break;
                case 4:
                    ++frequency4;
                    break;
                case 5:
                    ++frequency5;
                    break;
                case 6:
                    ++frequency6;
                    break;
            }
        }

        JTextArea outputArea = new JTextArea( 7, 10 );

        outputArea.setText(
                "Face\tFrequency" +
                        "\n1\t" + frequency1 +
                        "\n2\t" + frequency2 +
                        "\n3\t" + frequency3 +
                        "\n4\t" + frequency4 +
                        "\n5\t" + frequency5 +
                        "\n6\t" + frequency6 );

        JOptionPane.showMessageDialog( null, outputArea,
                "Rolling a Die 6000 Times",
                JOptionPane.INFORMATION_MESSAGE );
        System.exit( 0 );
    }
}

运行结果：

1. SquareInt

源代码：

public class SquareInt {

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

        for (int x = 1; x <= 10; x++) {
            result = square(x);
            // Math����Ҳ�ṩ����ƽ�����ķ���
            // result=(int)Math.pow(x,2);
            System.out.println("The square of " + x + " is " + result + "\n");
        }
    }

    // �Զ�����ƽ�����ľ�̬����
    public static int square(int y) {
        return y * y;
    }
}

运行结果：

"C:\Program Files\Java\jdk-17\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\lib\idea_rt.jar=6029:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\郑盾\IdeaProjects\test9_15\out\production\test9_15 SquareInt

The square of 1 is 1

The square of 2 is 4

The square of 3 is 9

The square of 4 is 16

The square of 5 is 25

The square of 6 is 36

The square of 7 is 49

The square of 8 is 64

The square of 9 is 81

The square of 10 is 100

Process finished with exit code 0

1. TestMath

源代码：

public class TestMath {

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

        for (int x = 1; x <= 10; x++) {
            result = square(x);
            // Math����Ҳ�ṩ����ƽ�����ķ���
            // result=(int)Math.pow(x,2);
            System.out.println("The square of " + x + " is " + result + "\n");
        }
    }

    // �Զ�����ƽ�����ľ�̬����
    public static int square(int y) {
        return y * y;
    }
}

运行结果：

"C:\Program Files\Java\jdk-17\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\lib\idea_rt.jar=6096:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\郑盾\IdeaProjects\test9_15\out\production\test9_15 TestMath

The square of 1 is 1

The square of 2 is 4

The square of 3 is 9

The square of 4 is 16

The square of 5 is 25

The square of 6 is 36

The square of 7 is 49

The square of 8 is 64

The square of 9 is 81

The square of 10 is 100

Process finished with exit code 0

1. TestRandom：

源代码：

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));
        //����0.0~1.0֮���α���double��
        System.out.println("rand.nextDouble()��" + rand.nextDouble());
        //����0.0~1.0֮���α���float��
        System.out.println("rand.nextFloat()��" + rand.nextFloat());
        //����ƽ��ֵ�� 0.0����׼���� 1.0��α��˹��
        System.out.println("rand.nextGaussian()��" + rand.nextGaussian());
        //����һ������long����ȡֵ��Χ��α�������
        System.out.println("rand.nextInt()��" + rand.nextInt());
        //����0~26֮���α�������
        System.out.println("rand.nextInt(26)��" + rand.nextInt(26));
        //����һ������long����ȡֵ��Χ��α�������
        System.out.println("rand.nextLong()��" +  rand.nextLong());
    }
}

运行结果：

"C:\Program Files\Java\jdk-17\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\lib\idea_rt.jar=6160:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\郑盾\IdeaProjects\test9_15\out\production\test9_15 TestRandom

rand.nextBoolean()��false

[94, -109, 52, -2, 57, 117, -70, 123, -36, 24, -119, 75, -22, 13, -57, 113]

rand.nextDouble()��0.45637749845199027

rand.nextFloat()��0.48870128

rand.nextGaussian()��-0.3014148748267904

rand.nextInt()��-1936491288

rand.nextInt(26)��23

rand.nextLong()��5193037278871421307

Process finished with exit code 0

1. TestSeed

源代码：

import java.util.Random;

public class TestSeed
{
    public static void main(String[] args)
    {
        Random r1 = new Random(50);
        System.out.println("��һ������Ϊ50��Random����");
        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("�ڶ�������Ϊ50��Random����");
        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("����Ϊ100��Random����");
        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("�Ե�ǰʱ��Ϊ���ӵ�Random����");
        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：

"C:\Program Files\Java\jdk-17\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\lib\idea_rt.jar=6224:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\郑盾\IdeaProjects\test9_15\out\production\test9_15 TestSeed

��һ������Ϊ50��Random����

r1.nextBoolean():   true

r1.nextInt():            -1727040520

r1.nextDouble():     0.6141579720626675

r1.nextGaussian():  2.377650302287946

---------------------------

�ڶ�������Ϊ50��Random����

r2.nextBoolean():   true

r2.nextInt():            -1727040520

r2.nextDouble():     0.6141579720626675

r2.nextGaussian():  2.377650302287946

---------------------------

����Ϊ100��Random����

r3.nextBoolean():   true

r3.nextInt():            -1139614796

r3.nextDouble():     0.19497605734770518

r3.nextGaussian():  0.6762208162903859

�Ե�ǰʱ��Ϊ���ӵ�Random����

r3.nextBoolean():   true

r3.nextInt():            -240417621

r3.nextDouble():     0.8432567576867095

r3.nextGaussian():  2.383733724521367

Process finished with exit code 0

1. VariableArgumentsTest

源代码：

public class VariableArgumentsTest {

    public static double max(double...values)
    {
        double largest=Double.MIN_VALUE;
        for (double v:values)
            if(v>largest) largest=v;
        return largest;
    }

    public static void main(String args[]) {

        System.out.println("Max:"+max(1,11,300,2,3));

    }
}

运行结果：

"C:\Program Files\Java\jdk-17\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\lib\idea_rt.jar=6288:C:\Program Files\JetBrains\IntelliJ IDEA 2023.1.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\郑盾\IdeaProjects\test9_15\out\production\test9_15 VariableArgumentsTest

Max:300.0

Process finished with exit code 012

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