isEmpty

public static boolean isEmpty(CharSequence cs)

常用函數之一，判斷字符串是否為""或者null

StringUtils.isEmpty(null) = trueStringUtils.isEmpty("") = trueStringUtils.isEmpty(" ") = falseStringUtils.isEmpty("bob") = falseStringUtils.isEmpty(" bob ") = false

isNotEmpty

public static boolean isNotEmpty(CharSequence cs)

最常用函數之一，跟上面方法相對

StringUtils.isNotEmpty(null) = falseStringUtils.isNotEmpty("") = falseStringUtils.isNotEmpty(" ") = trueStringUtils.isNotEmpty("bob") = trueStringUtils.isNotEmpty(" bob ") = true

isAnyEmpty

public static boolean isAnyEmpty(CharSequence... css)

任意一個參數為空的話，返回true， 如果這些參數都不為空的話返回false。

在寫一些判斷條件的時候，這個方法還是很實用的。

StringUtils.isAnyEmpty(null) = trueStringUtils.isAnyEmpty(null, "foo") = trueStringUtils.isAnyEmpty("", "bar") = trueStringUtils.isAnyEmpty("bob", "") = trueStringUtils.isAnyEmpty(" bob ", null) = trueStringUtils.isAnyEmpty(" ", "bar") = falseStringUtils.isAnyEmpty("foo", "bar") = false

isNoneEmpty

public static boolean isNoneEmpty(CharSequence... css)

任意一個參數是空，返回false 所有參數都不為空，返回true

注意這些方法的用法

StringUtils.isNoneEmpty(null) = falseStringUtils.isNoneEmpty(null, "foo") = falseStringUtils.isNoneEmpty("", "bar") = falseStringUtils.isNoneEmpty("bob", "") = falseStringUtils.isNoneEmpty(" bob ", null) = falseStringUtils.isNoneEmpty(" ", "bar") = trueStringUtils.isNoneEmpty("foo", "bar") = true

isBlank

public static boolean isBlank(CharSequence cs)

判斷字符對象是不是空字符串，注意與isEmpty的區別

StringUtils.isBlank(null) = trueStringUtils.isBlank("") = trueStringUtils.isBlank(" ") = trueStringUtils.isBlank("bob") = falseStringUtils.isBlank(" bob ") = false

isNotBlank

public static boolean isNotBlank(CharSequence cs)

原理同上

StringUtils.isNotBlank(null) = falseStringUtils.isNotBlank("") = falseStringUtils.isNotBlank(" ") = falseStringUtils.isNotBlank("bob") = trueStringUtils.isNotBlank(" bob ") = true

isAnyBlank

public static boolean isAnyBlank(CharSequence... css) StringUtils.isAnyBlank(null) = trueStringUtils.isAnyBlank(null, "foo") = trueStringUtils.isAnyBlank(null, null) = trueStringUtils.isAnyBlank("", "bar") = trueStringUtils.isAnyBlank("bob", "") = trueStringUtils.isAnyBlank(" bob ", null) = trueStringUtils.isAnyBlank(" ", "bar") = trueStringUtils.isAnyBlank("foo", "bar") = false

isNoneBlank

public static boolean isNoneBlank(CharSequence... css) StringUtils.isNoneBlank(null) = falseStringUtils.isNoneBlank(null, "foo") = falseStringUtils.isNoneBlank(null, null) = falseStringUtils.isNoneBlank("", "bar") = falseStringUtils.isNoneBlank("bob", "") = falseStringUtils.isNoneBlank(" bob ", null) = falseStringUtils.isNoneBlank(" ", "bar") = falseStringUtils.isNoneBlank("foo", "bar") = true

trim

public static String trim(String str)

移除字符串兩端的空字符串，制表符char <= 32如：\n \t 如果為空的話，返回空

如果為""

StringUtils.trim(null) = nullStringUtils.trim("") = ""StringUtils.trim(" ") = ""StringUtils.trim("abc") = "abc"StringUtils.trim(" abc ") = "abc"

變體有

public static String trimToNull(String str) public static String trimToEmpty(String str)

不常用，跟trim()方法類似

strip

public static String strip(String str) public static String strip(String str, String stripChars)

str：被處理的字符串，可為空 stripChars： 刪除的字符串，

StringUtils.strip(null, *) = nullStringUtils.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)

字符串比對方法，是比較實用的方法之一，兩個比較的字符串都能為空，不會報空指針異常。

StringUtils.equals(null, null) = trueStringUtils.equals(null, "abc") = falseStringUtils.equals("abc", null) = falseStringUtils.equals("abc", "abc") = trueStringUtils.equals("abc", "ABC") = false

equalsIgnoreCse

public static boolean equalsIgnoreCase(CharSequence str1, CharSequence str2)

上面方法的變體 字符串比較（忽略大小寫），在驗證碼……等字符串比較，真是很實用。

StringUtils.equalsIgnoreCase(null, null) = true StringUtils.equalsIgnoreCase(null, "abc") = false StringUtils.equalsIgnoreCase("abc", null) = false StringUtils.equalsIgnoreCase("abc", "abc") = true StringUtils.equalsIgnoreCase("abc", "ABC") = true

indexOf

public static int indexOf(CharSequence seq, int searchChar)

indexOf這個方法不必多說，這個方法主要處理掉了空字符串的問題，不會報空指針，有一定用處

StringUtils.indexOf(null, *) = -1StringUtils.indexOf("", *) = -1StringUtils.indexOf("aabaabaa", 'a') = 0StringUtils.indexOf("aabaabaa", 'b') = 2

ordinalIndexOf

public static int ordinalIndexOf(CharSequence str, CharSequence searchStr, int ordinal)

字符串在另外一個字符串里，出現第Ordinal次的位置

StringUtils.ordinalIndexOf(null, *, *) = -1StringUtils.ordinalIndexOf(*, null, *) = -1StringUtils.ordinalIndexOf("", "", *) = 0StringUtils.ordinalIndexOf("aabaabaa", "a", 1) = 0StringUtils.ordinalIndexOf("aabaabaa", "a", 2) = 1StringUtils.ordinalIndexOf("aabaabaa", "b", 1) = 2StringUtils.ordinalIndexOf("aabaabaa", "b", 2) = 5StringUtils.ordinalIndexOf("aabaabaa", "ab", 1) = 1StringUtils.ordinalIndexOf("aabaabaa", "ab", 2) = 4StringUtils.ordinalIndexOf("aabaabaa", "", 1) = 0StringUtils.ordinalIndexOf("aabaabaa", "", 2) = 0

lastIndexOf

public static int lastIndexOf(CharSequence seq, int searchChar)

字符串最后一次出現的位置

StringUtils.lastIndexOf(null, *) = -1StringUtils.lastIndexOf("", *) = -1StringUtils.lastIndexOf("aabaabaa", 'a') = 7StringUtils.lastIndexOf("aabaabaa", 'b') = 5

lastOrdinalIndexOf

public static int lastOrdinalIndexOf(CharSequence str, CharSequence searchStr, int ordinal)

字符串searchStr在str里面出現倒數第ordinal出現的位置

StringUtils.lastOrdinalIndexOf(null, *, *) = -1StringUtils.lastOrdinalIndexOf(*, null, *) = -1StringUtils.lastOrdinalIndexOf("", "", *) = 0StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 1) = 7StringUtils.lastOrdinalIndexOf("aabaabaa", "a", 2) = 6StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 1) = 5StringUtils.lastOrdinalIndexOf("aabaabaa", "b", 2) = 2StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 1) = 4StringUtils.lastOrdinalIndexOf("aabaabaa", "ab", 2) = 1StringUtils.lastOrdinalIndexOf("aabaabaa", "", 1) = 8StringUtils.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, *) = falseStringUtils.contains("", *) = falseStringUtils.contains("abc", 'a') = trueStringUtils.contains("abc", 'z') = false

containsAny

public static boolean containsAny(CharSequence cs, char... searchChars)

包含后面數組中的任意對象，返回true

StringUtils.containsAny(null, *) = falseStringUtils.containsAny("", *) = falseStringUtils.containsAny(*, null) = falseStringUtils.containsAny(*, []) = falseStringUtils.containsAny("zzabyycdxx",['z','a']) = trueStringUtils.containsAny("zzabyycdxx",['b','y']) = trueStringUtils.containsAny("aba", ['z']) = false

substring

public static String substring(String str, int start)

字符串截取

StringUtils.substring(null, *) = nullStringUtils.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)

這三個方法類似都是截取字符串

split

public static String[] split(String str, String separatorChars)

字符串分割

StringUtils.split(null, *) = nullStringUtils.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 static <T> String join(T... elements)

字符串連接

StringUtils.join(null) = nullStringUtils.join([]) = ""StringUtils.join([null]) = ""StringUtils.join(["a", "b", "c"]) = "abc"StringUtils.join([null, "", "a"]) = "a"

join

public static String join(Object[] array, char separator)

特定字符串連接數組，很多情況下還是蠻實用，不用自己取拼字符串

StringUtils.join(null, *) = nullStringUtils.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)

刪除空格

StringUtils.deleteWhitespace(null) = nullStringUtils.deleteWhitespace("") = ""StringUtils.deleteWhitespace("abc") = "abc"StringUtils.deleteWhitespace(" ab c ") = "abc"

removeStart

public static String removeStart(String str, String remove)

刪除以特定字符串開頭的字符串，如果沒有的話，就不刪除。

StringUtils.removeStart(null, *) = nullStringUtils.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)

生成訂單號，的時候還是很實用的。右邊自動補齊。

StringUtils.rightPad(null, *, *) = nullStringUtils.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)

左邊自動補齊

StringUtils.leftPad(null, *, *) = nullStringUtils.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)

將字符在某特定長度下，句子

StringUtils.center(null, *) = nullStringUtils.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)

首字母大寫

StringUtils.capitalize(null) = nullStringUtils.capitalize("") = ""StringUtils.capitalize("cat") = "Cat"StringUtils.capitalize("cAt") = "CAt"

swapCase

public static String swapCase(String str)

反向大小寫

StringUtils.swapCase(null) = nullStringUtils.swapCase("") = ""StringUtils.swapCase("The dog has a BONE") = "tHE DOG HAS A bone"

isAlpha

public static boolean isAlpha(CharSequence cs)

判斷字符串是否由字母組成

StringUtils.isAlpha(null) = falseStringUtils.isAlpha("") = falseStringUtils.isAlpha(" ") = falseStringUtils.isAlpha("abc") = trueStringUtils.isAlpha("ab2c") = falseStringUtils.isAlpha("ab-c") = false

defaultString

public static String defaultString(String str, String defaultStr)

默認字符串，相當于三目運算，前面弱為空，則返回后面一個參數

StringUtils.defaultString(null, "NULL") = "NULL"StringUtils.defaultString("", "NULL") = ""StringUtils.defaultString("bat", "NULL") = "bat"

reverse

public static String reverse(String str)

字符串翻轉

StringUtils.reverse(null) = nullStringUtils.reverse("") = ""StringUtils.reverse("bat") = "tab"

abbreviate

public static String abbreviate(String str, int maxWidth)

縮略字符串， 省略號要占三位。maxWith小于3位會報錯。

StringUtils.abbreviate(null, *) = nullStringUtils.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)

縮略字符串的一些高級用法

StringUtils.abbreviate(null, *, *) = nullStringUtils.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) = IllegalArgumentExceptionStringUtils.abbreviate("abcdefghij", 5, 6) = IllegalArgumentException

warp

public static String wrap(String str, char wrapWith)

包裝，用后面的字符串對前面的字符串進行包裝

StringUtils.wrap(null, *) = nullStringUtils.wrap("", *) = ""StringUtils.wrap("ab", '\0') = "ab"StringUtils.wrap("ab", 'x') = "xabx"StringUtils.wrap("ab", '\'') = "'ab'"StringUtils.wrap("\"ab\"", '\"') = "\"\"ab\"\""

轉載于:https://my.oschina.net/tensai/blog/3012993

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