Guava使用（一）Strings扩展

发布日期: 2020-01-14

文章字数: 407

阅读时长: 2 分

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Joiner

字符串连接

// 跳过空值
 String skipNulls = Joiner.on(",")
                .skipNulls()
                .join("张三", "李四", "王五");
        System.out.println(skipNulls);//张三,李四,王五

        String useNUll = Joiner
                .on(",")
                .useForNull("null") //空替换
                .join("张三",null, "李四", "王五");
        System.out.println(useNUll);//张三,null,李四,王五

Splitter

作用：字符串分隔
原因：JDK自带的split()函数，会默认忽略尾部的分隔符，StringTokenizer 会用五个空字符代替。

 String[] split = ",a,,b,".split(","); // "", "a", "", "b"

Iterable<String> split1 = Splitter.on(',')
                .trimResults()
                .omitEmptyStrings()
                .split("foo,bar,,   qux");
        System.out.println(split1.toString()); //[foo, bar, qux]

// 任意字符进行拆分
Iterable<String> split1 = Splitter.on(CharMatcher.anyOf(",;."))
                .trimResults()
                .omitEmptyStrings()
                .split("foo,bar,,   qux;23.,s");

API	作用	示例
Splitter.on(char)		Splitter.on(‘;’)
Splitter.on(CharMatcher)	以任意字符进行拆分	Splitter.on(CharMatcher.BREAKING_WHITESPACE) Splitter.on(CharMatcher.anyOf(“;,.”))
Splitter.on(String)		Splitter.on(“, “)
Splitter.on(Pattern)
Splitter.onPattern(String)		Splitter.onPattern(“\r?\n”)
Splitter.fixedLength(int)		Splitter.fixedLength(3)

方法	描述	示例
omitEmptyStrings()	Automatically omits empty strings from theresult.	Splitter.on(‘,’).omitEmptyStrings().split(“a,,c,d”)returns “a”, “c”, “d”
trimResults()	Trims whitespace from the results; equivalent to trimResults(CharMatcher.WHITESPACE).	Splitter.on(‘,’).trimResults().split(“a, b, c, d”) returns “a”, “b”, “c”, “d”
trimResults(CharMatcher)	Trims characters matching the specified CharMatcher from results.	Splitter.on(‘,’).trimResults(CharMatcher.is(‘‘)).split(“_a ,_b ,c__”) returns “a “, “b_ “, “c”.
limit(int)	Stops splitting after the specified number of strings have beenreturned.	Splitter.on(‘,’).limit(3).split(“a,b,c,d”) returns “a”, “b”, “c,d”

其它split方法

splitToList
splitToStream

CharMatcher

提供了字符串替换等操作
CharMatcher.is(‘a’).replaceFrom(“yaha”, “oo”) // return yoohoo
如果要调用的字符串只有一个字符，最好直接使用 replaceFrom(CharSequence, char)

Charsets

    bytes = string.getBytes(Charsets.UTF_8);

CaseFormat

字符格式化

   @Test
    public void testCaseFormat () {
 //       小驼峰 constantName
        CaseFormat.UPPER_UNDERSCORE.to(CaseFormat.LOWER_CAMEL, "CONSTANT_NAME");
//        连接 constant-name
        CaseFormat.UPPER_UNDERSCORE.to(CaseFormat.LOWER_HYPHEN, "CONSTANT_NAME");
//         constant_name
        CaseFormat.UPPER_UNDERSCORE.to(CaseFormat.LOWER_UNDERSCORE, "CONSTANT_NAME");
//           大驼峰 ConstantName
        CaseFormat.UPPER_UNDERSCORE.to(CaseFormat.UPPER_CAMEL, "CONSTANT_NAME");
//          CONSTANT_NAME
        CaseFormat.UPPER_UNDERSCORE.to(CaseFormat.UPPER_UNDERSCORE, "CONSTANT_NAME");
    }