org.springframework.util.StringUtils 工具类的使用
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