day06-数组

数组

1、数组概述

2、数组的声明创建

内存分析

数组三种初始化

数组的是个基本特点

数组边界

报错代码

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 8
	at com.kuang.array.ArrayDemo02.main(ArrayDemo02.java:10)

3、数组使用

For-Each循环

package com.kuang.array;

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

        //JDK1.5，没有下标
        for(int array : arrays){
            System.out.println(array);
        }
    }
}

数组作为方法入参

package com.kuang.array;

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


    //打印数组元素
    public static void printArray(int[] arrays){
        for (int i = 0; i < arrays.length; i++) {
            System.out.print(arrays[i]+" ");
        }
    }

}

数组作为返回值

package com.kuang.array;

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


    //打印数组元素
    public static void printArray(int[] arrays){
        for (int i = 0; i < arrays.length; i++) {
            System.out.print(arrays[i]+" ");
        }
    }

    //反转数组
    public static int[] reverse(int[] arrays){
        int[] result = new int[arrays.length];

        //反转的操作
        for (int i = 0 , j = result.length-1; i < arrays.length; i++,j--) {
            result[j] = arrays[i];
        }
        return result;
    }
}

4、多维数组

5、Arrays类

冒泡排序

6、稀疏数组

package com.kuang.array;

public class ArrayDemo08 {
    public static void main(String[] args) {
        //1、创建一个二维数组11*11  0：没有棋子  1：黑棋  2：白旗
        int[][] array1 = new int[11][11];
        array1[1][2] = 1;
        array1[2][3] = 2;
        //输出原始数组
        System.out.println("输出原始的数组");

        for(int[] ints : array1){
            for (int anInt : ints) {
                System.out.print(anInt+"\t");
            }
            System.out.println();
        }
        System.out.println("=====================");

        //转换为稀疏数组保存
        //获取有效值的个数
        int sum = 0;
        for (int i = 0; i < 11; i++) {
            for (int j = 0; j < 11; j++) {
                if (array1[i][j] != 0) {
                    sum++;
                }
            }
        }
        System.out.println("有效值的个数："+sum);

        //2、创建一个稀疏数组
        int[][] array2 = new int[sum+1][3];

        array2[0][0] = 11;
        array2[0][1] = 11;
        array2[0][2] = sum;

        //遍历二维数组，将非零的值，存放稀疏数组中
        int count = 0;
        for (int i = 0; i < array1.length; i++) {
            for (int j = 0; j < array1[i].length; j++) {
                if (array1[i][j] != 0) {
                    count++;
                    array2[count][0] = i;
                    array2[count][1] = j;
                    array2[count][2] = array1[i][j];
                }
            }
        }

        //输出稀疏数组
        System.out.println("稀疏数组");

        for (int i = 0; i < array2.length; i++) {
            System.out.println(array2[i][0]+"\t"+array2[i][1]+"\t"+array2[i][2]+"\t");

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

        //1、读取稀疏数组
        int[][] array3 = new int[array2[0][0]][array2[0][1]];

        //2、给其中的元素还原它的值
        for (int i = 1; i < array2.length; i++) {
            array3[array2[i][0]][array2[i][1]] = array2[i][2];
        }
        //3、打印
        System.out.println("输出还原的数组");

        for (int[] ints : array3) {
            for (int anInt : ints) {
                System.out.print(anInt+"\t");
            }
            System.out.println();
        }
    }
}