Java 字符串、数组、ArrayList之间的相互转换

1. 数组转字符串

import java.util.Arrays;

public class Test02 {
    public static void main(String[] args){
        String[] scores1 = new String[]{"10","20","30","40","50"};
        String[] scores2 = {"10","20","30","40","50"};

        // 数组转字符串
        // 1.第一种方法
        String str = Arrays.toString(scores1);
        System.out.println(str); // [10, 20, 30, 40, 50]
        // 2.第二种方法
        String str2 = "";
        for (int i = 0; i < scores1.length; i++) {
            str2 += scores1[i] + ",";
        }
        str2 = str2.substring(0, str2.length() - 1);
        System.out.println(str2); // 10,20,30,40,50
        // 3.第三种方法（相比第二种，更推荐第三种）
        StringBuilder stringBuilder = new StringBuilder();
        for (String score : scores1) {
            stringBuilder.append(score).append(",");
        }
        // String str3 = new StringBuilder(stringBuilder.substring(0, stringBuilder.length() - 1)).toString();
        String str3 = stringBuilder.toString().substring(0, stringBuilder.length() - 1);
        System.out.println(str3); // 10,20,30,40,50
　　}
}

2. 数组转ArrayList

import java.util.Arrays;

public class Test02 {
    public static void main(String[] args){
        // 数组转ArrayList
        String[] scores1 = new String[]{"10","20","30","40","50"};
        // 1.第一种方法
        ArrayList<String> arrayList = new ArrayList<String>(Arrays.asList(scores1));
        System.out.println(arrayList); // [10, 20, 30, 40, 50]

        List<String> list = Arrays.asList(scores1);
        System.out.println(list); // [10, 20, 30, 40, 50]
        // 2.第二种方法
        List<String> list2 = new ArrayList<String>();
        for(String score : scores1){
            list2.add(score);
        }
　　}
}

3. ArrayList转数组

import java.util.Arrays;

public class Test02 {
    public static void main(String[] args){
        // ArrayList转数组
        List<String> list = new ArrayList(){{add("10");add("20");add("30");add("40");add("50");}};
        System.out.println(list); // [10, 20, 30, 40, 50]

        //使用toArray(T[] a)方法
        String[] arrayList = list.toArray(new String[0]);
        System.out.println(Arrays.toString(arrayList)); // [10, 20, 30, 40, 50]
　　}
}

 4. ArrayList转字符串

public class Test02 {
    public static void main(String[] args){
        // ArrayList转字符串
        List<String> list = new ArrayList(){{add("10");add("20");add("30");add("40");add("50");}};
        System.out.println(list); // [10, 20, 30, 40, 50]

        String str = list.toString();
        System.out.println(str); // [10, 20, 30, 40, 50]
　　}
}

5. 字符串转数组

import java.util.Arrays;

public class Test02 {
    public static void main(String[] args){
        // 字符串转数组
        String str = "10,20,30,40,50";
        String[] strArr = str.split(",");
        System.out.println(Arrays.toString(strArr)); // [10, 20, 30, 40, 50]
　　}
}