1.直接复制以下代码运行查看运行结果

import java.util.ArrayList;
import java.util.List;
import java.util.StringJoiner;

public class Test {
    public static void main(String[] args) throws Exception {
        List<String> strs = new ArrayList<>();
        strs.add("abc");
        strs.add("def");
        strs.add("ghi");
        strs.add("jkl");
        strs.add("mno");
        strs.add("pqr");
        String t = "#";//拼接操作符号
        String join1 = String.join(t, strs);
        System.out.println("join1 = " + join1);
        StringJoiner sj = new StringJoiner(t);
        strs.forEach(sj::add);
        System.out.println("sj = " + sj);
        StringBuilder builder = new StringBuilder(t);
        strs.forEach(builder::append);
        System.out.println("builder = " + builder);
        StringBuffer buffer = new StringBuffer(t);
        strs.forEach(buffer::append);
        System.out.println("buffer = " + buffer);
    }

}

四种方法的运行结果都一样，不过推荐使用StringJoiner