CommonLang3中的StringUtils最全解析
2016-08-03 16:06
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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
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
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
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
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
public static boolean isNotBlank(CharSequence cs)
StringUtils.isNotBlank(null) = false StringUtils.isNotBlank("") = false StringUtils.isNotBlank(" ") = false StringUtils.isNotBlank("bob") = true StringUtils.isNotBlank(" bob ") = true原理同上
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
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
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
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"
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
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) = true StringUtils.equalsIgnoreCase(null, "abc") = false StringUtils.equalsIgnoreCase("abc", null) = false StringUtils.equalsIgnoreCase("abc", "abc") = true StringUtils.equalsIgnoreCase("abc", "ABC") = true
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
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
public static int lastIndexOf(CharSequence seq,int searchChar)
字符串最后一次出现的位置
StringUtils.lastIndexOf(null, *) = -1StringUtils.lastIndexOf("", *) = -1StringUtils.lastIndexOf("aabaabaa", 'a') = 7StringUtils.lastIndexOf("aabaabaa", 'b') = 5
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, *, *) = -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
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
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, *) = falseStringUtils.containsAny("", *) = falseStringUtils.containsAny(*, null) = falseStringUtils.containsAny(*, []) = falseStringUtils.containsAny("zzabyycdxx",['z','a']) = trueStringUtils.containsAny("zzabyycdxx",['b','y']) = trueStringUtils.containsAny("aba", ['z']) = false
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"
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
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"]
public static <T> String join(T... elements)
字符串连接
StringUtils.join(null) = nullStringUtils.join([]) = ""StringUtils.join([null]) = ""StringUtils.join(["a", "b", "c"]) = "abc"StringUtils.join([null, "", "a"]) = "a"
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, *) = 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"
public static String deleteWhitespace(String str)
删除空格
StringUtils.deleteWhitespace(null) = nullStringUtils.deleteWhitespace("") = ""StringUtils.deleteWhitespace("abc") = "abc"StringUtils.deleteWhitespace(" ab c ") = "abc"
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, *) = 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"
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, *, *) = 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"
public static String leftPad(String str,int size,char padChar)
左边自动补齐
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"
public static String center(String str,int size)
将字符在某特定长度下,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 "
public static String capitalize(String str)
首字母大写
StringUtils.capitalize(null) = nullStringUtils.capitalize("") = ""StringUtils.capitalize("cat") = "Cat"StringUtils.capitalize("cAt") = "CAt"
public static String swapCase(String str)
反向大小写
StringUtils.swapCase(null) = nullStringUtils.swapCase("") = ""StringUtils.swapCase("The dog has a BONE") = "tHE DOG HAS A bone"
public static boolean isAlpha(CharSequence cs)
判断字符串是否由字母组成
StringUtils.isAlpha(null) = falseStringUtils.isAlpha("") = falseStringUtils.isAlpha(" ") = falseStringUtils.isAlpha("abc") = trueStringUtils.isAlpha("ab2c") = falseStringUtils.isAlpha("ab-c") = false
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"
public static String reverse(String str)
字符串翻转
StringUtils.reverse(null) = nullStringUtils.reverse("") = ""StringUtils.reverse("bat") = "tab"
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, *) = 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)
缩略字符串的一些高级用法
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
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, *) = nullStringUtils.wrap("", *) = ""StringUtils.wrap("ab", '\0') = "ab"StringUtils.wrap("ab", 'x') = "xabx"StringUtils.wrap("ab", '\'') = "'ab'"StringUtils.wrap("\"ab\"", '\"') = "\"\"ab\"\""
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