Java基础学习（4）

数组的基本操作

package stl;

import java.util.Scanner;//导入扫描器

public class HelloWorld {
    
    
    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);
        //静态初始化
        int[] ages = {
    
    12, 24, 35, 22};
        double[] scores = {
    
    89.9, 23.7, 40, 10};
        for (int i = 0; i <= ages.length - 1; i++) {
    
    
            System.out.println(ages[i]);
        }
        System.out.println(scores);//[D@1d81eb93
        //动态初始化，遍历读入数据
        int n = scanner.nextInt();
        int[] arr = new int[n];
        for (int j = 0; j <= n - 1; j++) {
    
    
            arr[j] = scanner.nextInt();
        }
        for (int k = 0; k <= n - 1; k++) {
    
    
            System.out.print(arr[k]+" ");
        }
    }
}

结果

12
24
35
22
[D@1d81eb93
>>> 2
>>> 3
>>> 4
3 4 

自定义函数

自定义函数有返回值

package stl;

import java.util.Scanner;

public class HelloWorld {
    
    
    public static int sum(int a, int b) {
    
    //public static暂时固定不变
        int c = a + b;
        return c;
        //return后面一定不要写语句因为执行不到！
    }

    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);
        int a = scanner.nextInt();
        int b = scanner.nextInt();
        System.out.println(sum(a, b));
    }
}

自定义函数无返回值

public static void is_even(int num) {
    
    
        if (num % 2 == 0) {
    
    
            System.out.println("even");
        } else {
    
    
            System.out.println("not even");
        }
    }
    public static void main(String[] args) {
    
    
    Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        is_even(n);
    }

数组动态初始化+自定义函数选最大值

package stl;

import java.util.Scanner;

public class HelloWorld {
    
    
    public static int getmax(int[] arr) {
    
    
        int max = arr[0];
        for (int i = 1; i < arr.length; i++) {
    
    
            if (arr[i] > max) {
    
    
                max = arr[i];
            }
        }
        return max;
    }

    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] ages = new int[50];
        for (int i = 0; i < n; i++) {
    
    
            ages[i] = scanner.nextInt();
        }
        System.out.println(getmax(ages));
    }
}

自定义函数打印数组内容

package stl;

import java.util.Scanner;

public class HelloWorld {
    
    
    public static void print_arr(int[] arr, int len) {
    
    
        for (int i = 0; i < len - 1; i++) {
    
    
            System.out.print(arr[i] + " ");
        }
        System.out.print(arr[len - 1] + "\n");
    }

    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int[] ages = new int[50];
        for (int i = 0; i < n; i++) {
    
    
            ages[i] = scanner.nextInt();
        }
        print_arr(ages, n);
    }
}

中断

return;//立即停止并跳出当前方法