Java：数组的使用

• 普通的For循环
• For-Each循环（增强型For循环）
• 数组作方法入参
• 数组作返回值

package com.jiemyx.array;

public class ArrayDemo04 {
    public static void main(String[] args) {
        int[] arrays = {1,2,3,4,5};

        //打印全部的数组元素
        for (int i = 0; i < arrays.length; i++) {
            System.out.println(arrays[i]);
        }

        System.out.println("============");

        //计算所有元素的和
        int sum = 0;
        for (int i = 0; i < arrays.length; i++) {
            sum = sum + arrays[i];
        }
        System.out.println(sum);

        System.out.println("=============");

        //查找最大元素
        int max = arrays[0];
        for (int i = 1; i < arrays.length; i++) {
            if (max < arrays[i]){
                max = arrays[i];
            }
        }
        System.out.println(max);
    }
}

package com.jiemyx.array;

public class ArrayDemo05 {
    public static void main(String[] args) {
        int[] a = {1,2,3,4,5,6};

        //JDK1.5开始有的增强型for循环，但是没有下标
        for (int i : a) {
            System.out.println(i);
        }

        System.out.println("==========");

        //打印数组元素的方法
        printArray(a);

        System.out.println();
        System.out.println("============");

        //反转数组
        int[] b = reverse(a);
        printArray(b);
    }

    //数组作方法入参：定义一个打印数组元素的方法
    public static void printArray(int[] arrays){
        for (int i = 0; i < arrays.length; i++) {
            System.out.print(arrays[i] + " ");
        }
    }

    //数组作返回值：反转数组
    public static int[] reverse(int[] arrays){
        int[] result = new int[arrays.length];
        for (int i = 0,j = result.length-1; i < arrays.length; i++,j--) {
            result[j] = arrays[i];
        }
        return result;
    }
}

package com.jiemyx.array;

public class ArrayDemo06 {
    public static void main(String[] args) {
        int[] a = {1,4,2,8,0};

        //排序数组
        /*int b = a[0];
        for (int i = 1; i < a.length; i++) {
            if (a[0]<a[i]){
                a[0] = a[i];
                a[i] = b;
                b = a[0];
            }
        }

        b = a[1];
        for (int i = 2; i < a.length ; i++) {
            if (a[1]<a[i]){
                a[1] = a[i];
                a[i] = b;
                b = a[1];
            }
        }

        b = a[2];
        for (int i = 3; i < a.length ; i++) {
            if (a[2]<a[i]){
                a[2] = a[i];
                a[i] = b;
                b = a[2];
            }
        }

        b = a[3];
        for (int i = 4; i < a.length ; i++) {
            if (a[3]<a[i]){
                a[3] = a[i];
                a[i] = b;
                b = a[3];
            }
        }

        b = a[4];
        for (int i = 4; i < a.length ; i++) {
            if (a[4]<a[i]){
                a[4] = a[i];
                a[i] = b;
                b = a[4];
            }
        }*/

        for (int j = 0; j < a.length; j++) {
            int b = a[j];
            for (int i = j+1; i < a.length; i++) {
                if (a[j]<a[i]){
                    a[j] = a[i];
                    a[i] = b;
                    b = a[j];
                }
            }
        }

        for (int i : a) {
            System.out.println(i);
        }
    }
}