Guava字符串处理Joiner、Splitter

1、连接Joiner

用分隔符连接字符串时，如果字符串中途含有null，操作起来会需要特殊处理，Guava中提供的Joiner让字符串连接更简洁。

//链接字符串并忽略null,否则存在null报空指针异常
Joiner joiner = Joiner.on("|").skipNulls();
String result = joiner.join("one", null, "two", "three");
结果：one|two|three

//useForNull(String)方法可以给定某个字符串来替换null，而不像skipNulls()方法是直接忽略null。
Joiner joiner = Joiner.on("|").useForNull("12345");
String result = joiner.join("one", null, "two", "three");
结果：one|12345|two|three

//Joiner也可以用来连接对象类型，它会把对象的toString()的值连接起来。
List list = Arrays.asList("one", "two", "three");
结果：one|two|three

2、拆分Splitter

//String.split方法会自动省略最后一个字符串
String data = ",1,2,,3,";
String[] array =data.split(",");
结果为："","1","2","","3"

Splitter splitter = Splitter.on(",");
Iterable<String> iterable = splitter.split(data);
结果为："","1","2","","3",""

其它常用方法：

omitEmptyStrings() 从结果中自动忽略空字符串

trimResults() 移除结果字符串的前导空白和尾部空白

trimResults(CharMatcher) 给定匹配器，移除结果字符串的匹配字符

limit(int) 限制拆分出的字符串数量