JAVA--数组扩容练习

package learnday3.xiti;
//       Arrays.copyof(原数组，新数组的空间大小）

import java.util.Arrays;

public class Kuorong {
    public static void main(String[] args) {
        int[] arr = {1,2,3,4};
        int[] newArr = Arrays.copyOf(arr,10);

        arr = newArr;
        System.out.println(Arrays.toString(arr));
    }
}

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package learnday3.xiti;

import java.util.Arrays;

public class Xiti06 {
    public static void main(String[] args) {
        String[] arr1 = {"a","b","c"};
        String[] arr2 = new String[5];
        arr2[0] = "abc";
        arr2[1] = "abc";
        arr2[2] = "abc";
        System.out.println(Arrays.toString(arr2));
        //获得arr2的剩余空间
        int length = arr2.length;
        int count = 0;
        for (String s : arr2) {
            if(s==null){
                break;
            }count++;
        }
        int leftSpace = length - count;//arr2数组里面的剩余空间
        int len1 = arr1.length;//arr1的元素个数
        if(len1>leftSpace){//arr2剩余空间不够
            //扩大arr2空间-->扩容
            String[] newArray = new String[(len1+ count)*2];//自定义的length
            //循环将arr2的元素存储到newArray
            for (int i = 0; i < count; i++) {
                newArray[i]=arr2[i];
            }
            //更改了arr2的内存大小，引用数据类型赋值为内存地址值
            arr2 = newArray;
        }
        for(String s1:arr1){
            arr2[count++] = s1;
        }
        System.out.println("arr2:"+Arrays.toString(arr2));
    }
}