isEmpty
public static boolean isEmpty(CharSequence cs)
常用函数之一，判断字符串是否为""或者null
StringUtils.isEmpty(null) = true StringUtils.isEmpty("") = true StringUtils.isEmpty(" ") = false StringUtils.isEmpty("bob") = false StringUtils.isEmpty(" bob ") = false isNotEmpty
public static boolean isNotEmpty(CharSequence cs)
最常用函数之一，跟上面方法相对
StringUtils.isNotEmpty(null) = false StringUtils.isNotEmpty("") = false StringUtils.isNotEmpty(" ") = true StringUtils.isNotEmpty("bob") = true StringUtils.isNotEmpty(" bob ") = true isAnyEmpty
public static boolean isAnyEmpty(CharSequence... css)
任意一个参数为空的话，返回true， 如果这些参数都不为空的话返回false。
在写一些判断条件的时候，这个方法还是很实用的。
StringUtils.isAnyEmpty(null) = true StringUtils.isAnyEmpty(null, "foo") = true StringUtils.isAnyEmpty("", "bar") = true StringUtils.isAnyEmpty("bob", "") = true StringUtils.isAnyEmpty(" bob ", null) = true StringUtils.isAnyEmpty(" ", "bar") = false StringUtils.isAnyEmpty("foo", "bar") = false isNoneEmpty
public static boolean isNoneEmpty(CharSequence... css)
任意一个参数是空，返回false 所有参数都不为空，返回true
注意这些方法的用法
StringUtils.isNoneEmpty(null) = false StringUtils.isNoneEmpty(null, "foo") = false StringUtils.isNoneEmpty("", "bar") = false StringUtils.isNoneEmpty("bob", "") = false StringUtils.isNoneEmpty(" bob ", null) = false StringUtils.isNoneEmpty(" ", "bar") = true StringUtils.isNoneEmpty("foo", "bar") = true isBlank
public static boolean isBlank(CharSequence cs)
判断字符对象是不是空字符串，注意与isEmpty的区别
StringUtils.isBlank(null) = true StringUtils.isBlank("") = true StringUtils.isBlank(" ") = true StringUtils.isBlank("bob") = false StringUtils.isBlank(" bob ") = false isNotBlank
public static boolean isNotBlank(CharSequence cs)
原理同上
StringUtils.isNotBlank(null) = false StringUtils.isNotBlank("") = false StringUtils.isNotBlank(" ") = false StringUtils.isNotBlank("bob") = true StringUtils.isNotBlank(" bob ") = true isAnyBlank
public static boolean isAnyBlank(CharSequence... css)
StringUtils.isAnyBlank(null) = true StringUtils.isAnyBlank(null, "foo") = true StringUtils.isAnyBlank(null, null) = true StringUtils.isAnyBlank("", "bar") = true StringUtils.isAnyBlank("bob", "") = true StringUtils.isAnyBlank(" bob ", null) = true StringUtils.isAnyBlank(" ", "bar") = true StringUtils.isAnyBlank("foo", "bar") = false isNoneBlank
public static boolean isNoneBlank(CharSequence... css)
StringUtils.isNoneBlank(null) = false StringUtils.isNoneBlank(null, "foo") = false StringUtils.isNoneBlank(null, null) = false StringUtils.isNoneBlank("", "bar") = false StringUtils.isNoneBlank("bob", "") = false StringUtils.isNoneBlank(" bob ", null) = false StringUtils.isNoneBlank(" ", "bar") = false StringUtils.isNoneBlank("foo", "bar") = true trim
public static String trim(String str)
移除字符串两端的空字符串，制表符char <= 32如：\n \t 如果为空的话，返回空
如果为""
StringUtils.trim(null) = null StringUtils.trim("") = "" StringUtils.trim(" ") = "" StringUtils.trim("abc") = "abc" StringUtils.trim(" abc ") = "abc" 变体有
public static String trimToNull(String str)public static String trimToEmpty(String str)
不常用，跟trim()方法类似
strip
public static String strip(String str)public static String strip(String str, String stripChars)
str：被处理的字符串，可为空 stripChars： 删除的字符串，
StringUtils.strip(null, *) = null StringUtils.strip("", *) = "" StringUtils.strip("abc", null) = "abc" StringUtils.strip(" abc", null) = "abc" StringUtils.strip("abc ", null) = "abc" StringUtils.strip(" abc ", null) = "abc" StringUtils.strip(" abcyx", "xyz") = " abc" equals
public static boolean equals(CharSequence cs1, CharSequence cs2)
字符串比对方法，是比较实用的方法之一，两个比较的字符串都能为空，不会报空指针异常。
StringUtils.equals(null, null) = true StringUtils.equals(null, "abc") = false StringUtils.equals("abc", null) = false StringUtils.equals("abc", "abc") = true StringUtils.equals("abc", "ABC") = false equalsIgnoreCse
public static boolean equalsIgnoreCase(CharSequence str1, CharSequence str2)
上面方法的变体 字符串比较（忽略大小写），在验证码……等字符串比较，真是很实用。
StringUtils.equalsIgnoreCase(null, null) = trueStringUtils.equalsIgnoreCase(null, "abc") = falseStringUtils.equalsIgnoreCase("abc", null) = falseStringUtils.equalsIgnoreCase("abc", "abc") = trueStringUtils.equalsIgnoreCase("abc", "ABC") = true indexOf
public static int indexOf(CharSequence seq, int searchChar)
indexOf这个方法不必多说，这个方法主要处理掉了空字符串的问题，不会报空指针，有一定用处
StringUtils.indexOf(null, *) = -1 StringUtils.indexOf("", *) = -1 StringUtils.indexOf("aabaabaa", 'a') = 0 StringUtils.indexOf("aabaabaa", 'b') = 2 ordinalIndexOf
public static int ordinalIndexOf(CharSequence str, CharSequence searchStr, int ordinal)
字符串在另外一个字符串里，出现第Ordinal次的位置
StringUtils.ordinalIndexOf(null, *, *) = -1 StringUtils.ordinalIndexOf(*, null, *) = -1 StringUtils.ordinalIndexOf("", "", *) = 0 StringUtils.ordinalIndexOf("aabaabaa", "a", 1) = 0 StringUtils.ordinalIndexOf("aabaabaa", "a", 2) = 1 StringUtils.ordinalIndexOf("aabaabaa", "b", 1) = 2 StringUtils.ordinalIndexOf("aabaabaa", "b", 2) = 5 StringUtils.ordinalIndexOf("aabaabaa", "ab", 1) = 1 StringUtils.ordinalIndexOf("aabaabaa", "ab", 2) = 4 StringUtils.ordinalIndexOf("aabaabaa", "", 1) = 0 StringUtils.ordinalIndexOf("aabaabaa", "", 2) = 0 lastIndexOf
public static int lastIndexOf(CharSequence seq, int searchChar)
字符串最后一次出现的位置
StringUtils.lastIndexOf(null, *) = -1 StringUtils.lastIndexOf("", *) = -1 StringUtils.lastIndexOf("aabaabaa", 'a') = 7 StringUtils.lastIndexOf("aabaabaa", 'b') = 5 lastOrdinalIndexOf
public static int lastOrdinalIndexOf(CharSequence str, CharSequence searchStr, int ordinal)
字符串searchStr在str里面出现倒数第ordinal出现的位置
StringUtils.lastOrdinalIndexOf(null, *, *) = -1 StringUtils.lastOrdinalIndexOf(*, null, *) = -1 StringUtils.lastOrdinalIndexOf("", "", *) = 0 StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 1) = 7 StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 2) = 6 StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 1) = 5 StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 2) = 2 StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 1) = 4 StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 2) = 1 StringUtils.lastOrdinalIndexOf("aabaabaa", "", 1) = 8 StringUtils.lastOrdinalIndexOf("aabaabaa", "", 2) = 8 contains
public static boolean contains(CharSequence seq, int searchChar)
字符串seq是否包含searchChar
StringUtils.contains(null, *) = false StringUtils.contains("", *) = false StringUtils.contains("abc", 'a') = true StringUtils.contains("abc", 'z') = false containsAny
public static boolean containsAny(CharSequence cs, char... searchChars)
包含后面数组中的任意对象，返回true
StringUtils.containsAny(null, *) = false StringUtils.containsAny("", *) = false StringUtils.containsAny(*, null) = false StringUtils.containsAny(*, []) = false StringUtils.containsAny("zzabyycdxx",['z','a']) = true StringUtils.containsAny("zzabyycdxx",['b','y']) = true StringUtils.containsAny("aba", ['z']) = false substring
public static String substring(String str, int start)
字符串截取
StringUtils.substring(null, *) = null StringUtils.substring("", *) = "" StringUtils.substring("abc", 0) = "abc" StringUtils.substring("abc", 2) = "c" StringUtils.substring("abc", 4) = "" StringUtils.substring("abc", -2) = "bc" StringUtils.substring("abc", -4) = "abc" left right mid
public static String left(String str, int len)public static String right(String str, int len)public static String mid(String str, int pos, int len)
这三个方法类似都是截取字符串
split
public static String[] split(String str, String separatorChars)
字符串分割
StringUtils.split(null, *) = null StringUtils.split("", *) = [] StringUtils.split("abc def", null) = ["abc", "def"] StringUtils.split("abc def", " ") = ["abc", "def"] StringUtils.split("abc def", " ") = ["abc", "def"] StringUtils.split("ab:cd:ef", ":") = ["ab", "cd", "ef"] join
public staticString join(T... elements)
字符串连接
StringUtils.join(null) = null StringUtils.join([]) = "" StringUtils.join([null]) = "" StringUtils.join(["a", "b", "c"]) = "abc" StringUtils.join([null, "", "a"]) = "a"
join
public static String join(Object[] array, char separator)
特定字符串连接数组，很多情况下还是蛮实用，不用自己取拼字符串
StringUtils.join(null, *) = null StringUtils.join([], *) = "" StringUtils.join([null], *) = "" StringUtils.join(["a", "b", "c"], ';') = "a;b;c" StringUtils.join(["a", "b", "c"], null) = "abc" StringUtils.join([null, "", "a"], ';') = ";;a"
deleteWhitespace
public static String deleteWhitespace(String str)
删除空格
StringUtils.deleteWhitespace(null) = null StringUtils.deleteWhitespace("") = "" StringUtils.deleteWhitespace("abc") = "abc" StringUtils.deleteWhitespace(" ab c ") = "abc" removeStart
public static String removeStart(String str, String remove)
删除以特定字符串开头的字符串，如果没有的话，就不删除。
StringUtils.removeStart(null, *) = null StringUtils.removeStart("", *) = "" StringUtils.removeStart(*, null) = * StringUtils.removeStart("www.domain.com", "www.") = "domain.com" StringUtils.removeStart("domain.com", "www.") = "domain.com" StringUtils.removeStart("www.domain.com", "domain") = "www.domain.com" StringUtils.removeStart("abc", "") = "abc" rightPad
public static String rightPad(String str, int size, char padChar)
生成订单号，的时候还是很实用的。右边自动补齐。
StringUtils.rightPad(null, *, *) = null StringUtils.rightPad("", 3, 'z') = "zzz" StringUtils.rightPad("bat", 3, 'z') = "bat" StringUtils.rightPad("bat", 5, 'z') = "batzz" StringUtils.rightPad("bat", 1, 'z') = "bat" StringUtils.rightPad("bat", -1, 'z') = "bat" leftPad
public static String leftPad(String str, int size, char padChar)
左边自动补齐
StringUtils.leftPad(null, *, *) = null StringUtils.leftPad("", 3, 'z') = "zzz" StringUtils.leftPad("bat", 3, 'z') = "bat" StringUtils.leftPad("bat", 5, 'z') = "zzbat" StringUtils.leftPad("bat", 1, 'z') = "bat" StringUtils.leftPad("bat", -1, 'z') = "bat" center
public static String center(String str, int size)
将字符在某特定长度下，句子
StringUtils.center(null, *) = null StringUtils.center("", 4) = " " StringUtils.center("ab", -1) = "ab" StringUtils.center("ab", 4) = " ab " StringUtils.center("abcd", 2) = "abcd" StringUtils.center("a", 4) = " a " capitalize
public static String capitalize(String str)
首字母大写
StringUtils.capitalize(null) = null StringUtils.capitalize("") = "" StringUtils.capitalize("cat") = "Cat" StringUtils.capitalize("cAt") = "CAt" swapCase
public static String swapCase(String str)
反向大小写
StringUtils.swapCase(null) = null StringUtils.swapCase("") = "" StringUtils.swapCase("The dog has a BONE") = "tHE DOG HAS A bone" isAlpha
public static boolean isAlpha(CharSequence cs)
判断字符串是否由字母组成
StringUtils.isAlpha(null) = false StringUtils.isAlpha("") = false StringUtils.isAlpha(" ") = false StringUtils.isAlpha("abc") = true StringUtils.isAlpha("ab2c") = false StringUtils.isAlpha("ab-c") = false defaultString
public static String defaultString(String str, String defaultStr)
默认字符串，相当于三目运算，前面弱为空，则返回后面一个参数
StringUtils.defaultString(null, "NULL") = "NULL" StringUtils.defaultString("", "NULL") = "" StringUtils.defaultString("bat", "NULL") = "bat" reverse
public static String reverse(String str)
字符串翻转
StringUtils.reverse(null) = null StringUtils.reverse("") = "" StringUtils.reverse("bat") = "tab" abbreviate
public static String abbreviate(String str, int maxWidth)
缩略字符串， 省略号要占三位。maxWith小于3位会报错。
StringUtils.abbreviate(null, *) = null StringUtils.abbreviate("", 4) = "" StringUtils.abbreviate("abcdefg", 6) = "abc..." StringUtils.abbreviate("abcdefg", 7) = "abcdefg" StringUtils.abbreviate("abcdefg", 8) = "abcdefg" StringUtils.abbreviate("abcdefg", 4) = "a..." StringUtils.abbreviate("abcdefg", 3) = IllegalArgumentException public static String abbreviate(String str, int offset, int maxWidth)
缩略字符串的一些高级用法
StringUtils.abbreviate(null, *, *) = null StringUtils.abbreviate("", 0, 4) = "" StringUtils.abbreviate("abcdefghijklmno", -1, 10) = "abcdefg..." StringUtils.abbreviate("abcdefghijklmno", 0, 10) = "abcdefg..." StringUtils.abbreviate("abcdefghijklmno", 1, 10) = "abcdefg..." StringUtils.abbreviate("abcdefghijklmno", 4, 10) = "abcdefg..." StringUtils.abbreviate("abcdefghijklmno", 5, 10) = "...fghi..." StringUtils.abbreviate("abcdefghijklmno", 6, 10) = "...ghij..." StringUtils.abbreviate("abcdefghijklmno", 8, 10) = "...ijklmno" StringUtils.abbreviate("abcdefghijklmno", 10, 10) = "...ijklmno" StringUtils.abbreviate("abcdefghijklmno", 12, 10) = "...ijklmno" StringUtils.abbreviate("abcdefghij", 0, 3) = IllegalArgumentException StringUtils.abbreviate("abcdefghij", 5, 6) = IllegalArgumentException warp
public static String wrap(String str, char wrapWith)
包装，用后面的字符串对前面的字符串进行包装
StringUtils.wrap(null, *) = null StringUtils.wrap("", *) = "" StringUtils.wrap("ab", '\0') = "ab" StringUtils.wrap("ab", 'x') = "xabx" StringUtils.wrap("ab", '\'') = "'ab'" StringUtils.wrap("\"ab\"", '\"') = "\"\"ab\"\""