Java零基础入门 8：Java数组

Posted 2021-12-12 哪 吒

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目录

一、数组

二、数组拷贝

1、拷贝数值类型

2、Object数组复制

3、多维数组复制

4、对象数组复制

三、clone()

1、基本数组类型clone()

 2、对象数组clone()

四、数组排序

---

一、数组

数组是一种数据结构，是用来存储同一类型值的集合。通过一个整形下标可以访问数组中的每一个值。

private static void test04(){
    String[] arr = new String[]{"哪吒","云韵","比比东","美杜莎"};
    for (int i = 0; i<arr.length;i++) {
        System.out.println(arr[i]);
    }
}

二、数组拷贝

1、拷贝数值类型

package com.nezha.javase;

import java.util.Arrays;

public class ArrayTest {
    public static void main(String[] args) {
        String[] arr = new String[]{"哪吒","云韵","比比东","美杜莎"};
        String[] arr2 = new String[4];
        for (int i = 0; i < arr.length; i++) {
            arr2[i] = arr[i];
        }
        System.out.println("拷贝数值类型：");
        System.out.println(Arrays.toString(arr));
        System.out.println(Arrays.toString(arr2));
        System.out.println("--------------修改后--------------------");
        arr2[0] = "纳兰嫣然";
        System.out.println(Arrays.toString(arr));
        System.out.println(Arrays.toString(arr2));
    }
}

2、Object数组复制

//如果是类型转换问题，获取整形
private static void getIntegerArrayFromObjectArray() {
    Object[] obj1 = { 1, 2, 3, "4", "5" };
    Integer[] obj2 = new Integer[5];
 
    try {
        System.arraycopy(obj1, 0, obj2, 0, obj1.length);
    } catch (Exception e) {
        System.out.println("transfer exception:"+e);
    }
    System.out.println(Arrays.toString(obj1));
    System.out.println(Arrays.toString(obj2));
}
 
//获取Object数组中的字符串类型数据
private static void getStringArrayFromObjectArray1() {
    Object[] obj3 = { 1, 2, 3, "4", "5" };
    String[] obj4 = new String[5];
    try {
        System.arraycopy(obj3, 2, obj4, 2, 3);
    } catch (Exception e) {
        //transfer exception:java.lang.ArrayStoreException
        System.out.println("transfer exception:"+e);
    }
    System.out.println(Arrays.toString(obj3));
    //[null, null, null, null, null]
    System.out.println(Arrays.toString(obj4));
}
 
//获取Object数组中的字符串类型数据
private static void getStringArrayFromObjectArray2() {
    Object[] obj3 = { 1, 2, 3, "4", "5" };
    String[] obj4 = new String[5];
    try {
        System.arraycopy(obj3, 3, obj4, 3, 2);
    } catch (Exception e) {
        System.out.println("transfer exception:"+e);
    }
    System.out.println(Arrays.toString(obj3));
    //[null, null, null, 4, 5]
    System.out.println(Arrays.toString(obj4));
    obj3[3] = "zhangssan";
    System.out.println("查看是浅复制还是深复制~~~~~");
    System.out.println(Arrays.toString(obj3));
    System.out.println(Arrays.toString(obj4));
}

3、多维数组复制

//多维数组
public static void twoArray() {
    int[] arr1 = {1, 2};
    int[] arr2 = {3, 4};
    int[] arr3 = {5, 6};
 
    int[][] src = new int[][]{arr1, arr2, arr3};
 
    print("原始模样：", src);
    int[][] dest = new int[3][];
    System.arraycopy(src, 0, dest, 0, 3);
 
    System.out.println("改变前");
    print("src = ", src);
    print("dest = ", dest);
 
    //原数组改变后观察新数组是否改变，改变->浅复制，不改变->深复制
    src[0][0] = -1;
 
    System.out.println("改变后");
    print("src = ", src);
    print("dest = ", dest);
}

4、对象数组复制

//对象复制
private static void beanCopy() {
    User user1 = new User("zs",18);
    User user2 = new User("ls",18);
    User user3 = new User("ww",18);
    User[] userArraySrc = {user1, user2, user3};
    User[] userArrayDest = new User[3];
    System.out.println("对象复制，原始模样："+Arrays.toString(userArraySrc));
    System.arraycopy(userArraySrc, 0, userArrayDest, 0, userArraySrc.length);
    System.out.println("userArrayDest," + Arrays.toString(userArrayDest));
    System.out.println("------------改变原对象------------------");
    userArraySrc[0] = new User("su",20);
    System.out.println("***" + Arrays.toString(userArraySrc));
    System.out.println("***" + Arrays.toString(userArrayDest));
}
 
//二维数组toString()
private static void print(String string, int[][] arr) {
    System.out.print(string);
    for (int[] a : arr) {
        for (int i : a) {
            System.out.print(i + " ");
        }
        System.out.print(",");
    }
    System.out.println();
}

三、clone()

protected native Object clone() throws CloneNotSupportedException;

clone()也是native方法，所以也是C语言实现的。

1、基本数组类型clone()

 2、对象数组clone()

四、数组排序

可以使用Arrays.sort()方法。

package com.nezha.javase;

import java.util.Arrays;

public class ArrayTest {
    public static void main(String[] args) {
        int[] a={2,4,-11,9,0};
        Arrays.sort(a);
        for(int i=0;i<a.length;i++){
            System.out.print(a[i]+"  ");//-11  0  2  4  9  
        }
    }
}

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