java中数组赋值机制、反转、扩容、缩减
数组赋值机制
1.基本数据类型赋值，这个值就是具体的数据，而且相互不影响。
int n1 = 2;
int n2 = n1; //n1=2;n2=2
2.数组在默认情况下是引用传递，赋的值是地址
int arr1[] = {1,2,3};
int arr2[] = arr1;
public class test{
public static void main(String[] args){
int arr1[] = {1,2,3};
int arr2[] = arr1;
arr2[2] = 10;
for(int i = 0; i < arr1.length;i++){
System.out.println(arr1[i]);
}
}
}
结果：
编写代码 实现数组拷贝（内容复制）
将int arr1[ ] = {10,20,30};拷贝到arr2数组
public class test{
public static void main(String[] args){
int arr1[] = {10,20,30};
int arr2[] = new int[arr1.length];
for(int i = 0; i < arr1.length;i++){
arr2[i] = arr1[i];
}
arr2[2] = 100;
System.out.println("=====arr1的元素====");
for(int i = 0; i < arr1.length;i++){
System.out.println(arr1[i]);
}
System.out.println("=====arr2的元素====");
for(int i = 0; i < arr2.length;i++){
System.out.println(arr2[i]);
}
}
}
数组反转
把数组的元素内容反转
arr {11,22,33,44,55,66}->arr{66,55,44,33,22,11}
public class test{
public static void main(String[] args){
int arr[] = {11,22,33,44,55,66};
int temp = 0;
int len = arr.length;
//1.a[0]和a[5]进行交换
//2.a[1]和a[4]进行交换
//3.a[2]和a[3]进行交换
//4.一共交换3次 = arr.length / 2
//5.每次交换时，对应的下标是 arr[i] 和 arr[arr.length-1-i]
for(int i = 0; i < len / 2; i++){
temp = arr[len - 1 - i];
arr[len - 1 - i] = arr[i];
arr[i] = temp;
}
System.out.println("==反转后数组==");
for(int i = 0; i < arr.length; i++){
System.out.print(arr[i]+" ");
}
}
}
public class test{
public static void main(String[] args){
int arr1[] = {11,22,33,44,55,66};
int arr2[] = new int[arr1.length];
for(int i = 0; i < arr1.length; i++){
arr2[i] = arr1[arr1.length-i-1];
}
arr1 = arr2;
System.out.println("==反转后数组==");
for(int i = 0; i < arr1.length; i++){
System.out.print(arr1[i]+" ");
}
}
}
数组添加（扩容）
实现动态的给数组添加元素效果，实现对数组扩容。
1）原始数组使用静态分配int arr[ ] = {1,2,3}
2)增加的元素4，直接放在数组的最后 arr = {1,2,3,4}
public class test{
public static void main(String[] args){
int arr1[] = {1,2,3};
int arr2[] = new int[arr1.length + 1];
for(int i = 0; i < arr1.length; i++){
arr2[i] = arr1[i];
}
arr2[arr1.length] = 4;
arr1 = arr2;
for(int i = 0; i < arr2.length; i++){
System.out.print(arr2[i]+" ");
}
}
}
3)用户可以通过如下方式来决定是否继续添加，添加成功，是否继续？y/n
import java.util.Scanner;
public class test{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
int arr1[] = {1,2,3};
char answer = ' ';
do{
int arr2[] = new int[arr1.length + 1];
for(int i = 0; i < arr1.length; i++){
arr2[i] = arr1[i];
}
System.out.print("请输入你要添加的元素：");
arr2[arr1.length] = sc.nextInt();
arr1 = arr2;
for(int i = 0; i < arr1.length; i++){
System.out.print(arr1[i]+" ");
}
System.out.println("");
System.out.println("是否继续添加元素，回答y/n");
answer = sc.next().charAt(0);
if(answer == 'n')
break;
}while(true);
}
}
数组缩减
有一个数组{1，2，3，4，5}，可以将该数组进行缩减，提示用户是否继续缩减，每次缩减最后那个元素。当只剩下最后一个元素，提示：不能再缩减。
import java.util.Scanner;
public class test{
public static void main(String[] args){
Scanner sc = new Scanner(System.in);
int arr1[] = {1,2,3,4,5};
char answer = ' ';
do{
int arr2[] = new int[arr1.length - 1];
for(int i = 0; i < arr1.length - 1; i++){
arr2[i] = arr1[i];
}
arr1 = arr2;
for(int i = 0; i < arr1.length; i++){
System.out.print(arr1[i]+" ");
}
System.out.println("是否继续缩减y/n");
answer = sc.next().charAt(0);
if(arr1.length == 1 || answer == 'n'){
System.out.println("不能再缩减");
break;
}
}while(true);
}
}
原文地址：https://blog.csdn.net/weixin_73230994/article/details/142744388
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