目录

数组的概述和静态初始化

数组的地址值和元素访问

数组的遍历

数组的动态初始化

数组练习

数组的概述和静态初始化

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package 数组;public class array1 {public static void main(String[] args){//格式//静态初始化//数据类型 [] 数组名 = new 数组类型[]{元素1，元素2}//姓名String [] name1 = new String[]{"12","13","14"};String [] name2 = {"12","13","14"};//年龄int [] age1 = new int[]{20,21,22};int [] age2 = {20,21,22};//身高double [] cm1 = new double[]{1.78,1.55,1.20};double [] cm2 = {1.78,1.55,1.20};}
}

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数组的地址值和元素访问

package 数组;public class array2 {public static void main(String[] args){//格式//静态初始化//数据类型 [] 数组名 = new 数组类型[]{元素1，元素2}//姓名String [] name1 = new String[]{"12","13","14"};String [] name2 = {"12","13","14"};//年龄int [] age1 = new int[]{20,21,22};int [] age2 = {20,21,22};//身高double [] cm1 = new double[]{1.78,1.55,1.20};double [] cm2 = {1.78,1.55,1.20};String number1 = name1[0];int number2 = age1[0];double number3 = cm1[0];System.out.println("我叫" + number1 + "!");System.out.println("今年" + number2 + "岁!");System.out.println("我的身高是" + number3 + "m!");System.out.println(name1[1]);age1[0] = 121;System.out.println(age1[0]);}
}

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数组的遍历

package 数组;import sun.security.util.Length;public class arraylx1 {public static void main(String[] args){/* 定义一个数组，存储1,2,3,4,5,6,7,8,9,10遍历数组得到每一个元素。
要求:
1，如果是奇数，则将当前数字扩大两倍
2，如果是偶数，则将当前数字变成二分之一
*/int number[] = {1,2,3,4,5,6,7,8,9,10};for (int i  =0 ; i < number.length ; i++){if (number[i] % 2 == 0){number[i] = number[i] / 2;}else{number[i] = number[i] * 2;}}for (int i = 0 ; i < number.length; i++){System.out.println(number[i]);}}
}

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数组的动态初始化

package 数组;public class array3 {public static void main(String[] args){int[] number = new int[50];number[0] = 1;number[1] = 2;number[2] = 3;System.out.println(number[0]);System.out.println(number[1]);System.out.println(number[2]);System.out.println(number[3]);}
}//数组默认初始化值的规律
//整数类型:默认初始化值0
//小数类型:默认初始化值0.0
//字符类型:默认初始化值 \ueeee’ 空格
//布尔类型:默认初始化值 false
//引用数据类型:默认初始化值 null

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数组练习

练习package 数组;import javafx.geometry.Bounds;import javax.swing.*;
import java.util.Random;public class arraylx2 {public static void main(String[] args) {/*需求:生成10个1~10之间的随机数存入数组1) 求出所有数据的和2)求所有数据的平均数3) 统计有多少个数据比平均值小*///定义数组int[] arr = new int[10];//把随机数存入数组Random r = new Random();for(int i = 0;i < arr.length;i++){int number = r.nextInt(100) + 1;arr[i] = number;}//1) 求出所有数据的和int num = 0;for (int i = 0; i < arr.length; i++) {num = num + arr[i];}System.out.println("所有数的和是" + num);//2)求所有数据的平均数int veg = 0;for (int i = 0; i < arr.length; i++) {veg = num / arr.length;}System.out.println("所有数据的平均数为" + veg);//3) 统计有多少个数据比平均值小int conent = 0;for (int i = 0; i < arr.length; i++) {if(arr[i] < veg){conent = conent + 1;//conent++}}System.out.println("有" + conent + "个数据比平均值小");for (int i = 0; i < arr.length; i++) {System.out.print(arr[i] + " ");}}
}

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package 数组;public class arraylx3 {public static void main(String[] args) {/*需求: 定义一个数组，存入1,2,3,4,5。交换首尾索引对应的元素.交换前: 1,2,3,4,5，交换后: 5,2,3,4,1*///定义数组存储数据int[] arr = {1, 2, 3, 4, 5};for (int i = 0, j = arr.length - 1; i < j; i++, j--) {int temp = arr[i];arr[i] = arr[j];arr[j] = temp;}for (int i = 0; i < arr.length; i++) {System.out.println(arr[i] + " ");}}
}