String. Join() and stringutils Join () gracefully solves the splicing of arrays or collections

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StringUtils.join()  Realization

pom rely on

api explain

Code implementation

String.join() Realization

pom rely on

api explain

Code implementation

Comparison of the two implementation methods

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You may have encountered an array or collection in a certain way “,”、“-”、“.” The need to splice characters into new strings , The spliced string will look like this   a,b,c perhaps a-b-c perhaps a.b.c etc. .

You might want to go through the splicing , Remove the last splice character .

public static void main(String[] args) {
    List<String> list = new ArrayList<>(Arrays.asList(new String[]{"a", "b", "c"}));
    StringBuilder stringBuilder = new StringBuilder();
    for (String s : list) {
        stringBuilder.append(s + ",");
    }
    System.out.println(stringBuilder.substring(0, stringBuilder.length() - 1));
}

Or think about traversing first , The last element of the array is handled separately .

public static void main(String[] args) {
    List<String> list = new ArrayList<>(Arrays.asList(new String[]{"a", "b", "c"}));
    StringBuilder stringBuilder = new StringBuilder();
    for (int i = 0; i < list.size() -1 ;i ++) {
        stringBuilder.append(list.get(i) + ",");
    }
    System.out.println(stringBuilder.append(list.get(list.size() - 1)).toString());
}

The above two methods either deal with the last spliced special character 、 Or you need to process the last character separately , Not particularly elegant , Do we have an elegant way to implement it . Don't say , There are really two ways to implement .

StringUtils.join()  Realization

pom rely on

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.11</version>
</dependency>

api explain

Code implementation

public static void main(String[] args) {
    List<String> list = new ArrayList<>(Arrays.asList(new String[]{"a", "b", "c"}));
    System.out.println(StringUtils.join(list, ","));
}

String.join() Realization

pom rely on

String.join() yes JDK8 The new method , No need to introduce external dependencies .

api explain

Code implementation

public static void main(String[] args) {
    List<String> list = new ArrayList<>(Arrays.asList(new String[]{"a", "b", "c"}));
    System.out.println(String.join(",", list));
}

StringUtils.join and  String.join() Both are one line of code and you're done , Is it elegant ？

Comparison of the two implementation methods

Parameter sequence ：StringUtils.join() The first parameter is an array or collection , The second parameter is the concatenation character ;String.join() The first parameter is the concatenation character , The second parameter array or collection .

Parameter range ：StringUtils.join() You can pass in Integer Or other types of collections or arrays ; String.join() You can pass in and implement charSequence A collection or array of interface types .

conclusion ： If it is a collection or array of string type, it is recommended to use String.join(), For other types, it is recommended to use  StringUtils.join().