Java日志第49天 2020.8.25

例4.1 在主函数中调用其他函数

public class Demo4_1 {
    public static void main(String[] args) {
        printstar();
        print_message();
        printstar();
    }

    private static void print_message() {
        System.out.println("Welcome to java!");
    }

    private static void printstar() {
        //输出30个"*"
        System.out.println("******************************");
    }
}

 

 

 

例4.2 调用函数时的数据传递

import java.util.Scanner;

public class Demo4_2 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int a, b, c;
        System.out.print("Please enter two integer nembers:");
        a = sc.nextInt();
        b = sc.nextInt();

        c = max(a, b);
        System.out.println("max="+c);
    }

    private static int max(int a, int b) {
        int z;
        z = a > b ? a : b;
        return z;
    }
}

 

 

例4.3 对被调用的函数做声明

import java.util.Scanner;

public class Demo4_3 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        float a, b, c;
        System.out.print("Please enter a, b:");
        a = sc.nextFloat();
        b = sc.nextFloat();

        c = add(a, b);
        System.out.println("sum = "+c);
    }

    private static float add(float a, float b) {
        return (a+b);
    }
}

 

 

例4.4 函数指定为内置函数

public class Demo4_4 {
    public static void main(String[] args) {
        int i = 10;
        int j = 20;
        int k = 30;
        int m;

        m = max(i, j, k);
        System.out.println("max = "+m);
    }

    public static final int max (int a,int b,int c) {
        if(b>a) {
            a = b;
        }
        if(c>a) {
            a = c;
        }
        return a;
    }
}

 

 

 

例4.5 求3个数中最大的数（分别考虑整数、双精度数、长整数的情况）

import java.util.Scanner;

public class Demo4_5 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int i1, i2, i3, i;
        i1 = sc.nextInt();
        i2 = sc.nextInt();
        i3 = sc.nextInt();
        i = max(i1,i2,i3);
        System.out.println("i_max = "+i);

        double d1, d2, d3, d;
        d1 = sc.nextDouble();
        d2 = sc.nextDouble();
        d3 = sc.nextDouble();
        d = max(d1,d2,d3);
        System.out.println("d_max = "+d);

        long g1, g2, g3, g;
        g1 = sc.nextLong();
        g2 = sc.nextLong();
        g3 = sc.nextLong();
        g = max(g1,g2,g3);
        System.out.println("g_max = "+g);
    }

    public static int max(int a, int b, int c){
        if (b>a)
            a=b;
        if (c>a)
            a=c;
        return a;
    }

    public static double max (double a, double b, double c) {
        if (b>a)
            a=b;
        if (c>a)
            a=c;
        return a;
    }

    public static long max(long a, long b, long c) {
        if (b>a)
            a=b;
        if (c>a)
            a=c;
        return a;
    }
}