用采集器#连接、前缀和后缀格式化字符串列表

方法Collector#joining被重载，参数CharSequence prefix, CharSequence suffix ，使List 格式化更容易。

import java.util.List;
import java.util.stream.Collectors;
import org.junit.jupiter.api.Test;


public class CollectorsJoiningTest {

    @Test
    public void withPrefixAndSuffix() {
        var words = List.of("java","duke","jvm");
        var message = words.stream().collect(Collectors.joining(",", "[", "]"));
        System.out.println(message);
    }
}

该单元测试打印。 [java,duke,jvm]