java学习笔记 2021.9.21

增强型数组（二层循环）

例如：数组名为array
array.for//第一层循环
ints.for//第二层循环

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

稀疏数组

package com.ye.array;

import java.util.Arrays;

public class Demo09 {
    public static void main(String[] args) {
        int[][] array1 = new int[11][11];
        array1[1][2]=1;
        array1[2][3]=2;
        array1[5][2]=3;
        array1[6][8]=9;
        //打印原数组
        for (int[] ints : array1) {
            for (int anInt : ints) {
                System.out.print(anInt+"\t");
            }
            System.out.println();
        }
        //打印有效值个数
        int sum = 0;
        for (int i = 0; i < array1.length; i++) {
            for (int j = 0; j < array1[i].length; j++) {
                if (array1[i][j]!=0){
                    sum++;
                }
            }
        }
        System.out.println(sum);

        int[][] array2 = new int[sum+1][3];
        array2[0][0]= 11;
        array2[0][1]= 11;
        array2[0][2]= sum;
        int count = 0;
        for (int i = 0; i < array1.length; i++) {
            for (int j = 0; j < array1.length; j++) {
                if (array1[i][j]!=0){
                    count++;
                    array2[count][0]=i;
                    array2[count][1]=j;
                    array2[count][2]=array1[i][j];
                }
            }
        }
        //打印稀疏数组
        for (int i = 0; i < array2.length; i++) {
            for (int j = 0; j < array2[i].length; j++) {
                System.out.print(array2[i][j]+" ");
            }
            System.out.println();
        }
        //还原稀疏数组
        int[][] array3 = new int[array2[0][0]][array2[0][1]];
        for (int i = 1; i < array2.length; i++) {
            for (int j = 0; j < array2[i].length; j++) {
                array3[array2[i][0]][array2[i][2]]=array2[i][2];
            }
        }
        //打印还原稀疏数组
        for (int[] ints : array3) {
            for (int anInt : ints) {
                System.out.print(anInt+"\t");
            }
            System.out.println();
        }


    }

}