数组概述

数组是相同类型数据的有序集合。 数组 描述的是相同类型的若干数据，按照一定的先后次序排列组合而成。 数组中的每一个数据称为一个元素，通过下标访问数组。

数组创建

package array; public class Demo01 { public static void main(String[] args) { int[] numbers; //1.声明一个数组 numbers = new int[10]; //2.分配空间 //3. 赋值 numbers[0] = 1; numbers[1] = 2; numbers[2] = 3; numbers[3] = 4; numbers[4] = 5; numbers[5] = 6; numbers[6] = 7; numbers[7] = 8; numbers[8] = 9; numbers[9] = 10; System.out.println(numbers[2]); int sum = 0; for (int i = 0; i <numbers.length ; i++) { sum += numbers[i]; } System.out.println("总和为：" + sum); } }

package array; public class Demo02 { public static void main(String[] args) { // 静态初始化 int[] a = {1,2,3,4,5}; Man[] man = {new Man(),new Man()}; //动态初始化 int[] b = new int[10]; b[0] = 10; System.out.println(b[0]); System.out.println(b[1]); } }

数组使用

package array; import java.sql.PreparedStatement; public class Demo03 { public static void main(String[] args) { int[] array = {1,2,3,4,5}; //遍历 for (int i = 0; i < array.length ; i++) { System.out.println(array[i]); } //求和 int sum = 0; for (int i = 0; i < array.length ; i++) { sum += array[i]; } System.out.println(sum); //找最大数 int max = array[0]; for (int i = 0; i <array.length ; i++) { if(array[i] > max){ max = array[i]; } } System.out.println(max); //for each for (int arr:array ) { System.out.println(arr); } //反转数组 int[] result = new int[array.length]; for (int i = 0, j = array.length-1; i < array.length; i++,j--) { result[i] = array[j]; } for (int res:result ) { System.out.println(res); } } }

多维数组

package array; public class Demo04 { public static void main(String[] args) { int[][] arrays = {{1,2,3},{4,5,6}}; for (int i = 0; i < 2 ; i++) { for (int j = 0; j <arrays[0].length ; j++) { System.out.println(arrays[i][j]); } } } }

Arrays类

package array; import java.util.Arrays; public class ArraysDemo { public static void main(String[] args) { int[] a = {1,2,5,3,343,56,43,45454}; System.out.println(Arrays.toString(a)); Arrays.sort(a); //排序，升序 System.out.println(Arrays.toString(a)); Arrays.fill(a,0); //填充 //Arrays.fill(a,2,3,4); System.out.println(Arrays.toString(a)); } public static void PrintArray(int[] a){ for (int i = 0; i <a.length ; i++) { if (i == 0) { System.out.print("["); } if (i == a.length - 1) { System.out.print(a[i] + "]"); } else { System.out.print(a[i] + ", "); } } } }

冒泡排序

package array; import java.util.Arrays; public class BubbleSort { public static void main(String[] args) { int[] a = {1,3,2,4,9,6,5,7,8}; System.out.println(Arrays.toString(a)); int[] sort = bubleSort(a); System.out.println(Arrays.toString(sort)); } public static int[] bubleSort(int[] a){ for (int i = 0; i <a.length-1 ; i++) { boolean flag = false; for (int j = 0; j <a.length-1-i; j++) { if(a[j]>a[j+1]){ int t = a[j]; a[j] = a[j+1]; a[j+1] = t; flag = true; } } if(flag==false){ break; } } return a; } }

稀疏数组

package array; import java.util.Arrays; //稀疏数组 public class xisushuzu { public static void main(String[] args) { int[][] a = new int[11][11]; a[1][2] = 1; a[2][3] =2; System.out.println("原始数组："); for (int[] arr:a) { for (int ar:arr) { System.out.print(ar+"\t"); } System.out.println(); } int count=0; for (int i = 0; i < a.length ; i++) { for (int j = 0; j <a[i].length; j++) { if(a[i][j]!=0){ count++; } } } int[][] xisu = new int[count+1][3]; xisu[0][0] = a.length; xisu[0][1] = a[0].length; xisu[0][2] = count; int k = 1; for (int i = 0; i < a.length ; i++) { for (int j = 0; j <a[i].length; j++) { if(a[i][j]!=0){ xisu[k][0] = i; xisu[k][1] = j; xisu[k][2] = a[i][j]; k++; } } } System.out.println("稀疏数组："); for (int i = 0; i <= count ; i++) { System.out.println(Arrays.toString(xisu[i])); } //稀疏数组还原 //1. 读取稀疏数组的值 int[][] arrr = new int[xisu[0][0]][xisu[0][1]]; for (int i = 1; i <xisu.length ; i++) { arrr[xisu[i][0]][xisu[i][1]] = xisu[i][2]; } System.out.println("还原数组:"); for (int[] br:arrr) { for (int b:br) { System.out.print(b+"\t"); } System.out.println(); } } }

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