一，非空判断

  1. StringUtils.isEmpty(null)      = true
  2. StringUtils.isEmpty("")        = true
  3. StringUtils.isEmpty(" ")       = false
  4. StringUtils.isEmpty("bob")     = false
  6. ---------------------------------------
  8. StringUtils.isBlank(null)      = true
  9. StringUtils.isBlank("")        = true
  10. StringUtils.isBlank(" ")       = true
  11. StringUtils.isBlank("bob")     = false

二，匹配

1，是否相等

  1. //是否相等
  2. StringUtils.equals(null, null)   = true
  3. StringUtils.equals(null, "abc")  = false
  4. StringUtils.equals("abc", null)  = false
  5. StringUtils.equals("abc", "abc") = true
  6. StringUtils.equals("abc", "ABC") = false
  8. ---------------------------------------    
  10. StringUtils.equalsIgnoreCase(null, null)   = true
  11. StringUtils.equalsIgnoreCase(null, "abc")  = false
  12. StringUtils.equalsIgnoreCase("abc", null)  = false
  13. StringUtils.equalsIgnoreCase("abc", "abc") = true
  14. StringUtils.equalsIgnoreCase("abc", "ABC") = true

2，包含其中

  1. StringUtils.contains(null, *)     = false
  2. StringUtils.contains(*, null)     = false
  3. StringUtils.contains("", "")      = true
  4. StringUtils.contains("abc", "")   = true
  5. StringUtils.contains("abc", "a")  = true
  6. StringUtils.contains("abc", "z")  = false

3，匹配头尾

  1. StringUtils.startsWith(null, null)      = true
  2. StringUtils.startsWith(null, "abc")     = false
  3. StringUtils.startsWith("abcdef", null)  = false
  4. StringUtils.startsWith("abcdef", "abc") = true
  5. StringUtils.startsWith("ABCDEF", "abc") = false
  8. StringUtils.endsWith(null, null)      = true
  9. StringUtils.endsWith(null, "def")     = false
  10. StringUtils.endsWith("abcdef", null)  = false
  11. StringUtils.endsWith("abcdef", "def") = true
  12. StringUtils.endsWith("ABCDEF", "def") = false
  13. StringUtils.endsWith("ABCDEF", "cde") = false
  14. StringUtils.endsWith("ABCDEF", "")    = true

4，命中位置

  1. StringUtils.indexOf(null, *)         = -1
  2. StringUtils.indexOf("", *)           = -1
  3. StringUtils.indexOf("aabaabaa", 'a') = 0
  4. StringUtils.indexOf("aabaabaa", 'b') = 2
  6. ---------------------------------------    
  8. StringUtils.lastIndexOf(null, *)         = -1
  9. StringUtils.lastIndexOf("", *)           = -1
  10. StringUtils.lastIndexOf("aabaabaa", 'a') = 7
  11. StringUtils.lastIndexOf("aabaabaa", 'b') = 5

5，命中数量

  1. StringUtils.countMatches(null, *)       = 0
  2. StringUtils.countMatches("", *)         = 0
  3. StringUtils.countMatches("abba", null)  = 0
  4. StringUtils.countMatches("abba", "")    = 0
  5. StringUtils.countMatches("abba", "a")   = 2
  6. StringUtils.countMatches("abba", "ab")  = 1
  7. StringUtils.countMatches("abba", "xxx") = 0

6，差异之处

  1. StringUtils.difference(null, null) = null
  2. StringUtils.difference("", "") = ""
  3. StringUtils.difference("", "abc") = "abc"
  4. StringUtils.difference("abc", "") = ""
  5. StringUtils.difference("abc", "abc") = ""
  6. StringUtils.difference("abc", "ab") = ""
  7. StringUtils.difference("ab", "abxyz") = "xyz"
  8. StringUtils.difference("abcde", "abxyz") = "xyz"
  9. StringUtils.difference("abcde", "xyz") = "xyz"

一，去除

1，去空格

  1. StringUtils.trim(null)          = null
  2. StringUtils.trim("")            = ""
  3. StringUtils.trim("     ")       = ""
  4. StringUtils.trim("abc")         = "abc"
  5. StringUtils.trim("    abc    ") = "abc"
  7. ---------------------------------------    
  9. StringUtils.trimToEmpty(null)          = ""
  10. StringUtils.trimToEmpty("")            = ""
  11. StringUtils.trimToEmpty("     ")       = ""
  12. StringUtils.trimToEmpty("abc")         = "abc"
  13. StringUtils.trimToEmpty("    abc    ") = "abc"

2，去换行符

  1. StringUtils.chop(null)          = null
  2. StringUtils.chop("")            = ""
  3. StringUtils.chop("abc \r")      = "abc "
  4. StringUtils.chop("abc\n")       = "abc"
  5. StringUtils.chop("abc\r\n")     = "abc"
  6. StringUtils.chop("abc")         = "ab"
  7. StringUtils.chop("abc\nabc")    = "abc\nab"
  8. StringUtils.chop("a")           = ""
  9. StringUtils.chop("\r")          = ""
  10. StringUtils.chop("\n")          = ""
  11. StringUtils.chop("\r\n")        = ""

3，去特定字符

  1. StringUtils.removeStart(null, *)      = null
  2. StringUtils.removeStart("", *)        = ""
  3. StringUtils.removeStart(*, null)      = *
  4. StringUtils.removeStart("www.domain.com", "www.")   = "domain.com"
  5. StringUtils.removeStart("domain.com", "www.")       = "domain.com"
  6. StringUtils.removeStart("www.domain.com", "domain") = "www.domain.com"
  7. StringUtils.removeStart("abc", "")    = "abc"
  9. ---------------------------------------    
  11. StringUtils.removeEnd(null, *)      = null
  12. StringUtils.removeEnd("", *)        = ""
  13. StringUtils.removeEnd(*, null)      = *
  14. StringUtils.removeEnd("www.domain.com", ".com.")  = "www.domain.com"
  15. StringUtils.removeEnd("www.domain.com", ".com")   = "www.domain"
  16. StringUtils.removeEnd("www.domain.com", "domain") = "www.domain.com"
  17. StringUtils.removeEnd("abc", "")    = "abc"    
  19. ---------------------------------------    
  21. StringUtils.remove(null, *)       = null
  22. StringUtils.remove("", *)         = ""
  23. StringUtils.remove("queued", 'u') = "qeed"
  24. StringUtils.remove("queued", 'z') = "queued"

三，转化

1，截取前N个

  1. StringUtils.truncate(null, 0)       = null
  2. StringUtils.truncate(null, 2)       = null
  3. StringUtils.truncate("", 4)         = ""
  4. StringUtils.truncate("abcdefg", 4)  = "abcd"
  5. StringUtils.truncate("abcdefg", 8)  = "abcdefg"

2，替换

  1. StringUtils.replaceOnce(null, *, *)        = null
  2. StringUtils.replaceOnce("", *, *)          = ""
  3. StringUtils.replaceOnce("any", null, *)    = "any"
  4. StringUtils.replaceOnce("any", *, null)    = "any"
  5. StringUtils.replaceOnce("any", "", *)      = "any"
  6. StringUtils.replaceOnce("aba", "a", null)  = "aba"
  7. StringUtils.replaceOnce("aba", "a", "")    = "ba"
  8. StringUtils.replaceOnce("aba", "a", "z")   = "zba"
  10. ---------------------------------------    
  12. StringUtils.replace(null, *, *)        = null
  13. StringUtils.replace("", *, *)          = ""
  14. StringUtils.replace("any", null, *)    = "any"
  15. StringUtils.replace("any", *, null)    = "any"
  16. StringUtils.replace("any", "", *)      = "any"
  17. StringUtils.replace("aba", "a", null)  = "aba"
  18. StringUtils.replace("aba", "a", "")    = "b"
  19. StringUtils.replace("aba", "a", "z")   = "zbz"

3，分割

  1. StringUtils.split(null, *)         = null
  2. StringUtils.split("", *)           = []
  3. StringUtils.split("a.b.c", '.')    = ["a", "b", "c"]
  4. StringUtils.split("a..b.c", '.')   = ["a", "b", "c"]
  5. StringUtils.split("a:b:c", '.')    = ["a:b:c"]
  6. StringUtils.split("a b c", ' ')    = ["a", "b", "c"]

4，合并

  1. StringUtils.join(null)            = null
  2. StringUtils.join([])              = ""
  3. StringUtils.join([null])          = ""
  4. StringUtils.join(["a", "b", "c"]) = "abc"
  5. StringUtils.join([null, "", "a"]) = "a"
  7. ---------------------------------------    
  9. StringUtils.join(null, *)               = null
  10. StringUtils.join([], *)                 = ""
  11. StringUtils.join([null], *)             = ""
  12. StringUtils.join(["a", "b", "c"], ';')  = "a;b;c"
  13. StringUtils.join(["a", "b", "c"], null) = "abc"
  14. StringUtils.join([null, "", "a"], ';')  = ";;a"

5，大小写

  1. StringUtils.upperCase(null)  = null
  2. StringUtils.upperCase("")    = ""
  3. StringUtils.upperCase("aBc") = "ABC"
  5. ---------------------------------------    
  7. StringUtils.lowerCase(null)  = null
  8. StringUtils.lowerCase("")    = ""
  9. StringUtils.lowerCase("aBc") = "abc"

四，比较

  1. str1.compareTo(str2)
  3. StringUtils.compare(null, null)   = 0
  4. StringUtils.compare(null , "a")   < 0
  5. StringUtils.compare("a", null)    > 0
  6. StringUtils.compare("abc", "abc") = 0
  7. StringUtils.compare("a", "b")     < 0
  8. StringUtils.compare("b", "a")     > 0
  9. StringUtils.compare("a", "B")     > 0
  10. StringUtils.compare("ab", "abc")  < 0