02-guava CharMatcher、Charsets、Strings

CharMatcher

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try{
        byte[] bytes = "foobarbaz".getBytes("UTF-8");
    }catch (UnsupportedEncodingException e){
        //This really can't happen UTF-8 must be supported
    }

简写:
byte[] bytes2 = "foobarbaz".getBytes(Charsets.UTF_8);

Strings

Strings类为使用字符串提供了一些方便的实用方法。

  • 字符填充

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    Strings.padEnd("foo", 6, 'x');//fooxxx
    Strings.padEnd("fooaaa", 6, 'x');//fooaaa

  • 空处理

nullToEmpty:这个方法接受一个字符串作为参数并返回
如果值不为空或长度大于0，则为原始字符串;否则
它返回空串

emptyToNull:该方法以类似于nullToEmpty的方式执行，
但如果字符串参数为空或者为null，则返回null

isNullOrEmpty:此方法对字符串执行空长检查
，如果该字符串实际上为null或空（长度为0）,则返回true

CharMatcher

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@Test
public void testRemoveWhiteSpace(){
    String tabsAndSpaces = "String with spaces and
    tabs";
    String expected = "String with spaces and tabs";
    String scrubbed = CharMatcher.WHITESPACE.
    collapseFrom(tabsAndSpaces,' ');
    assertThat(scrubbed,is(expected));
}

@Test
public void testTrimRemoveWhiteSpace(){
    String tabsAndSpaces = " String with spaces and
    tabs";
    String expected = "String with spaces and tabs";
    String scrubbed = CharMatcher.WHITESPACE.
    trimAndCollapseFrom(tabsAndSpaces,' ');
    assertThat(scrubbed,is(expected));
}

@Test
public void testRetainForm() {
    String letterAndNumbers = "foo989yxbar234";
    String expected = "989234";
    String retained = CharMatcher.JAVA_DIGIT.retainFrom(letterAndNumbers);
    Assert.assertThat(expected, is(retained));
}

来源：Getting Started with Google Guava