StringJoiner.setEmptyValue() - 设置默认值

使用 setEmptyValue()方法在 StringJoiner 中设置任何默认值。
我们可以使用此默认值查看计算后是否添加了任何元素。

StringJoiner joiner = new StringJoiner(",", "[", "]");
System.out.println(joiner.toString());

joiner.setEmptyValue("EMPTY");
System.out.println(joiner.toString());
joiner.add("hello");
joiner.add("on");
joiner.add("it");
joiner.add("road");
System.out.println(joiner.toString());

在 Java 8 中引入了 StringJoiner 类，用于以不同方式连接字符串。

带有分隔符、前缀和后缀的 StringJoiner 示例

在下面的示例中，我们使用逗号来连接字符串，前缀和后缀分别为[,]：
前缀和后缀是可选的。

StringJoiner joiner = new StringJoiner(",", "[", "]");

joiner.add("hello");
joiner.add("on");
joiner.add("it");
joiner.add("road");
joiner.add("java");
joiner.add("website");
String result = joiner.toString();
System.out.println(result);

输出:

[hello,on,it,road,java,website]

合并两个 StringJoiner

使用 StringJoiner.merge() 方法合并 StringJoiner的两个实例

//第1个 Joiner
StringJoiner joiner1 = new StringJoiner(",", "[", "]");

joiner1.add("hello");
joiner1.add("on");
joiner1.add("it");
joiner1.add("road");
joiner1.add("java");
joiner1.add("website");

//第2个 Joiner
StringJoiner joiner2 = new StringJoiner("-", "{", "}");
joiner2.add("python");
joiner2.add("php");
joiner2.add("asp");
joiner1.merge( joiner2 );
System.out.println( joiner1.toString() );	 
System.out.println( joiner2.toString() );