Spring的StringUtils工具类

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原文网址：《Spring的StringUtils工具类》

org.springframework.util.StringUtils

我们经常会对字符串进行操作，spring已经实现了常用的处理功能。我们可以使用org.springframework.util.StringUtils 工具类帮我们处理字符串。

工具类整理如下：

 StringUtils.hasLength(null) = false;
  StringUtils.hasLength("") = false;
  StringUtils.hasLength(" ") = true;
  StringUtils.hasLength("Hello") = true;  

  StringUtils.hasText(null) = false;
  StringUtils.hasText("") = false;
  StringUtils.hasText(" ") = false;
  StringUtils.hasText("12345") = true;
  StringUtils.hasText(" 12345 ") = true;  

  //是否包含空白字符
  StringUtils.containsWhitespace(null)=false;
  StringUtils.containsWhitespace("")=false;
  StringUtils.containsWhitespace("a")=false;
  StringUtils.containsWhitespace("abc")=false;
  StringUtils.containsWhitespace("abc")=false;
  StringUtils.containsWhitespace(" ")=true;
  StringUtils.containsWhitespace(" a")=true;
  StringUtils.containsWhitespace("abc ")=true;
  StringUtils.containsWhitespace("a b")=true
  StringUtils.containsWhitespace("a  b")  

  StringUtils.trimWhitespace(null)=null;
  StringUtils.trimWhitespace("")="";
  StringUtils.trimWhitespace(" ")="";
  StringUtils.trimWhitespace("/t")="";
  StringUtils.trimWhitespace(" a")="a";
  StringUtils.trimWhitespace("a ")="a";
  StringUtils.trimWhitespace(" a ")="a";
  StringUtils.trimWhitespace(" a b ")="a b";  

  StringUtils.trimLeadingWhitespace(null)=null;
  StringUtils.trimLeadingWhitespace("")="";
  StringUtils.trimLeadingWhitespace(" ")="";
  StringUtils.trimLeadingWhitespace("/t")="";
  StringUtils.trimLeadingWhitespace(" a")="a";
  StringUtils.trimLeadingWhitespace("a ")="a ";
  StringUtils.trimLeadingWhitespace(" a ")="a ";
  StringUtils.trimLeadingWhitespace(" a b ")="a b "
  StringUtils.trimLeadingWhitespace(" a b  c ")="a b  c "  

  StringUtils.trimTrailingWhitespace(null)=null;
  StringUtils.trimTrailingWhitespace(" ")="";
  StringUtils.trimTrailingWhitespace("/t")="";
  StringUtils.trimTrailingWhitespace("a ")="a";
  StringUtils.trimTrailingWhitespace(" a")=" a";
  StringUtils.trimTrailingWhitespace(" a ")=" a";
  StringUtils.trimTrailingWhitespace(" a b ")=" a b";
  StringUtils.trimTrailingWhitespace(" a b  c ")=" a b  c";  

  StringUtils.trimAllWhitespace("")="";
  StringUtils.trimAllWhitespace(" ")="";
  StringUtils.trimAllWhitespace("/t")="";
  StringUtils.trimAllWhitespace(" a")="a";
  StringUtils.trimAllWhitespace("a ")="a";
  StringUtils.trimAllWhitespace(" a ")="a";
  StringUtils.trimAllWhitespace(" a b ")="ab";
  StringUtils.trimAllWhitespace(" a b  c "="abc";
  // 统计一个子字符串在字符串出现的次数
  StringUtils.countOccurrencesOf(null, null) == 0;
  StringUtils.countOccurrencesOf("s", null) == 0;
  StringUtils.countOccurrencesOf(null, "s") == 0;
  StringUtils.countOccurrencesOf("erowoiueoiur", "WERWER") == 0;
  StringUtils.countOccurrencesOf("erowoiueoiur", "x")=0;
  StringUtils.countOccurrencesOf("erowoiueoiur", " ") == 0;
  StringUtils.countOccurrencesOf("erowoiueoiur", "") == 0;
  StringUtils.countOccurrencesOf("erowoiueoiur", "e") == 2;
  StringUtils.countOccurrencesOf("erowoiueoiur", "oi") == 2;
  StringUtils.countOccurrencesOf("erowoiueoiur", "oiu") == 2;
  StringUtils.countOccurrencesOf("erowoiueoiur", "oiur") == 1;
  StringUtils.countOccurrencesOf("erowoiueoiur", "r") == 2;  

  //字符串替换
  String inString = "a6AazAaa77abaa";
  String oldPattern = "aa";
  String newPattern = "foo";
  // Simple replace
  String s = StringUtils.replace(inString, oldPattern, newPattern);
  s.equals("a6AazAfoo77abfoo")=true;  

  // Non match: no change
  s = StringUtils.replace(inString, "qwoeiruqopwieurpoqwieur", newPattern);
  s.equals(inString)=true
  s = StringUtils.replace(inString, oldPattern, null);
  s.equals(inString)=true  

  // Null old pattern: should ignore
  s = StringUtils.replace(inString, null, newPattern);
         s.equals(inString)=true  

  //删除字符串
  String inString = "The quick brown fox jumped over the lazy dog";
  String noThe = StringUtils.delete(inString, "the");
  noThe.equals("The quick brown fox jumped over  lazy dog")=true;
  String nohe = StringUtils.delete(inString, "he");
  nohe.equals("T quick brown fox jumped over t lazy dog")=true;
  String nosp = StringUtils.delete(inString, " ");
  nosp.equals("Thequickbrownfoxjumpedoverthelazydog")=true;
  String killEnd = StringUtils.delete(inString, "dog");
  killEnd.equals("The quick brown fox jumped over the lazy ")=true;
  String mismatch = StringUtils.delete(inString, "dxxcxcxog");
   mismatch.equals(inString)=true;  

  //删除任何字符
  //源代码如下
  //char c = inString.charAt(i);
  //如果不存在 c 值，则返回 -1
  //if (charsToDelete.indexOf(c) == -1) {
  //out.append(c);
  //}  

  String inString = "Able was I ere I saw Elba";  

  String res = StringUtils.deleteAny(inString, "I");
         res.equals("Able was  ere  saw Elba")=true;
  res = StringUtils.deleteAny(inString, "AeEba!");
  res.equals("l ws I r I sw l")=true;
  String mismatch = StringUtils.deleteAny(inString, "#@$#$^");
  mismatch.equals(inString)=true;  

  //源代码如下 return (str != null ? "'" + str + "'" : null);
  assertEquals("'myString'", StringUtils.quote("myString"));
  assertEquals("''", StringUtils.quote(""));
  assertNull(StringUtils.quote(null));
  //将第一个字符改大写
  StringUtils.capitalize(Str)
  //将第一个个字符改小写
  StringUtils.uncapitalize(str)  

  //mypath/myfile.txt" -> "myfile.txt
  //获取字符串文件名和扩展名
  StringUtils.getFilename("myfile").equals("myfile")=true;
  StringUtils.getFilename("mypath/myfile".equals("myfile")=true;
  StringUtils.getFilename("mypath/myfile".equals("myfile")=true;
  StringUtils.getFilename("myfile.txt").equals("myfile.txt")=true;
  StringUtils.getFilename("mypath/myfile.txt").equals("myfile.txt")=true;  

  // 获取字符串扩展名,以.分隔
  StringUtils.getFilenameExtension("myfile")=null;
  StringUtils.getFilenameExtension("myPath/myfile")=null;
  StringUtils.getFilenameExtension("myfile.").equals("")=true;
  StringUtils.getFilenameExtension("myPath/myfile.").equals("")=true;
  StringUtils.StringUtils.getFilenameExtension("myfile.txt").equals("txt")=true;
  StringUtils.getFilenameExtension("mypath/myfile.txt").equals("txt")=true;  

  //舍去文件名扩展名
  StringUtils.stripFilenameExtension(null)=true;
  StringUtils.stripFilenameExtension("").equals("")=true;
  StringUtils.stripFilenameExtension("myfile").equals("myfile")=true;
  StringUtils.stripFilenameExtension("mypath/myfile").equals("mypath/myfile")=true;
  StringUtils.stripFilenameExtension("myfile.").equals("myfile")=true;
  StringUtils.stripFilenameExtension("mypath/myfile.").equals("mypath/myfile")=true;
  StringUtils.stripFilenameExtension("mypath/myfile.").equals("mypath/myfile")=true;
  StringUtils.stripFilenameExtension("myfile.txt").equals("myfile")=true;
  StringUtils.stripFilenameExtension("mypath/myfile.txt").equals("mypath/myfile")=true