Java8 List转变为逗号分隔的String

需求：Arrays.asList("AA", "BB") --> "AA,BB"

In Java 8

采用stream的方式

List<String> strList = Arrays.asList("AA","BB","CC");

String newStr = strList.stream().collect(Collectors.joining(","));

System.out.println("Output:" + newStr);// Output:AA,BB,CC

使用String.join()函数，给函数传递一个分隔符合一个迭代器，StringJoiner对象会帮助我们完成所有的事情

String newStr = String.join(",", strList);

System.out.println("Output:" + newStr);// Output:AA,BB,CC

In Java 7

Java 7的实现方法

List strList = Arrays.asList("AA","BB","CC");

StringBuilder sb = newStringBuilder();

for(inti =0; i < strList.size(); i++) {

    if(i !=0) {

        sb.append(",");

    }   

    sb.append(strList.get(i));

}

System.out.println("Output:"+ sb.toString());// Output:AA,BB,CC