String， int[]，Integer[] ，List＜Integer＞互转

小鱼儿 2024-03-23 10:11 81阅读 0赞

#### 这里写目录标题 ####

*  String，int\[\]互转
 *  String，Integer\[\]互转
 *  String，List＜Integer＞互转
 *  int\[\]，Integer\[\]互转
 *  int\[\]，List＜Integer＞互转
 *  Integer\[\]，List＜Integer＞互转
 *  核心如下四点

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## String，int\[\]互转 ##

// “1,2,3,4” → int[]
    String str = "1,2,3,4,5";
    int[] ints1 = Arrays.stream(str.split(",")).mapToInt(Integer::parseInt).toArray();
    
    
    // int[] → “1,2,4,5”
    int[] temp = {
        1, 2, 4, 5};
    String str1 = Arrays.stream(temp).boxed().map(String::valueOf).collect(Collectors.joining(","));
    String str2 = Arrays.stream(temp).mapToObj(String::valueOf).collect(Collectors.joining(","));

--------------------

## String，Integer\[\]互转 ##

// “1,2,3,4” → Integer[]
    String str = "1,2,3,4,5";
    Integer[] ints3 = Arrays.stream(str.split(",")).map(Integer::parseInt).toArray(Integer[]::new);
    Integer[] ints2 = Arrays.stream(str.split(",")).mapToInt(Integer::parseInt).boxed().toArray(Integer[]::new);
    
    // Integer[] →  “1,2,4,5”
    Integer[] temp = {
        1, 2, 4, 5};
    String collect = Arrays.stream(temp).map(String::valueOf).collect(Collectors.joining(","));

--------------------

## String，List＜Integer＞互转 ##

// “1,2,3,4”  →  List<Integer>
    String str = "1,2,3,4,5";
    List<Integer> list = Arrays.stream(str.split(",")).map(Integer::parseInt).collect(Collectors.toList());
    
    // List<Integer> →  “1,2,4,5”
    List<Integer> list1 = Arrays.asList(1, 2, 4, 5);
    String str = list1.stream().map(String::valueOf).collect(Collectors.joining(","));

--------------------

## int\[\]，Integer\[\]互转 ##

// int[] → Integer[]
    int[] ints11 = {
        1, 2, 3};
    Integer[] integers = Arrays.stream(ints11).boxed().toArray(Integer[]::new);
    
    // Integer[] → int[]
    int[] ints4 = Arrays.stream(integers).mapToInt(Integer::valueOf).toArray();
    int[] ints5 = Arrays.stream(integers).mapToInt(Integer::intValue).toArray();

--------------------

## int\[\]，List＜Integer＞互转 ##

// int[] -> List<Integer>
    int[] ints11 = {
        1, 2, 3};
    List<Integer> integerList = Arrays.stream(ints11).boxed().collect(Collectors.toList());
    List<Integer> integerList1 = Arrays.stream(ints11).boxed().toList();
    
    // List<Integer> -> int[]
    int[] ints1 = integerList.stream().mapToInt(Integer::intValue).toArray();

--------------------

## Integer\[\]，List＜Integer＞互转 ##

// Integer[] -> List<Integer>
    List<Integer> integers1 = Arrays.stream(integer11).collect(Collectors.toList());
    List<Integer> integers2 = Arrays.asList(integer11);
    List<Integer> integers3 = new ArrayList<>(Arrays.asList(integer11));
    
    // List<Integer> -> Integer[]
    Integer[] integers4 = integers2.toArray(Integer[]::new);
    Integer[] integers5 = integers2.toArray(new Integer[0]);
    Integer[] integers6 = integers2.toArray(new Integer[integers2.size()]);

--------------------

## 核心如下四点 ##

转int              .mapToInt(Integer::parseInt)       
    转Integer          .map(Integer::parseInt)       
    
    归约到int[]        .toArray()
    归约到Integer[]    .toArray(Integer[]::new)
    
    转String           .collect(Collectors.joining(","));