StringUtils工具类的使用

 一、数组转成字符串：
    1、 将数组中的字符转换为一个字符串
    将数组中的字符转换为一个字符串

    @param strToConv 要转换的字符串 ,默认以逗号分隔
    @return 返回一个字符串
    String[3] s={"a","b","c"}
    StringUtil.convString（s)="a,b,c"
    2、 static public String converString(String strToConv)
    @param strToConv 要转换的字符串 ,
    @param conv 分隔符,默认以逗号分隔
    @return 同样返回一个字符串

    String[3] s={"a","b","c"}
    StringUtil.convString（s,"@")="a@b@c"
    static public String converString(String strToConv, String conv)

    二、空值检测：
    3、

    Checks if a String is empty ("") or null.

    判断一个字符串是否为空，空格作非空处理。 StringUtils.isEmpty(null) = true StringUtils.isEmpty("") = true StringUtils.isEmpty(" ") = false StringUtils.isEmpty("bob") = false StringUtils.isEmpty(" bob ") = false

    NOTE: This method changed in Lang version 2.0.

    It no longer trims the String.
    That functionality is available in isBlank().

    @param str the String to check, may be null
    @return true if the String is empty or null
    public static boolean isEmpty(String str)

    三、非空处理：
    4、
    Checks if a String is not empty ("") and not null.

    判断一个字符串是否非空，空格作非空处理. StringUtils.isNotEmpty(null) = false StringUtils.isNotEmpty("") = false StringUtils.isNotEmpty(" ") = true StringUtils.isNotEmpty("bob") = true StringUtils.isNotEmpty(" bob ") = true

    @param str the String to check, may be null
    @return true if the String is not empty and not null
    public static boolean isNotEmpty(String str)

    5、

    Checks if a String is not empty (""), not null and not whitespace only.

    判断一个字符串是否非空，空格作空处理. StringUtils.isNotBlank(null) = false StringUtils.isNotBlank("") = false StringUtils.isNotBlank(" ") = false StringUtils.isNotBlank("bob") = true StringUtils.isNotBlank(" bob ") = true

    @param str the String to check, may be null
    @return true if the String is
    not empty and not null and not whitespace
    @since 2.0
    public static boolean isNotBlank(String str)

    四、 空格处理
    6、
    Removes control characters (char <= 32) from both

    ends of this String, handling null by returning
    null.

    The String is trimmed using {@link String#trim()}.

    Trim removes start and end characters <= 32.
    To strip whitespace use {@link //strip(String)}.

    To trim your choice of characters, use the

    {@link //strip(String, String)} methods.

    格式化一个字符串中的空格，有非空判断处理； StringUtils.trim(null) = null StringUtils.trim("") = "" StringUtils.trim(" ") = "" StringUtils.trim("abc") = "abc" StringUtils.trim(" abc ") = "abc"

    @param str the String to be trimmed, may be null
    @return the trimmed string, null if null String input
    public static String trim(String str)

    7、

    Removes control characters (char <= 32) from both

    ends of this String returning null if the String is
    empty ("") after the trim or if it is null.

    The String is trimmed using {@link String#trim()}.

    Trim removes start and end characters <= 32.
    To strip whitespace use {@link /stripToNull(String)}.

    格式化一个字符串中的空格，有非空判断处理，如果为空返回null； StringUtils.trimToNull(null) = null StringUtils.trimToNull("") = null StringUtils.trimToNull(" ") = null StringUtils.trimToNull("abc") = "abc" StringUtils.trimToNull(" abc ") = "abc"

    @param str the String to be trimmed, may be null
    @return the trimmed String,
    null if only chars <= 32, empty or null String input
    @since 2.0
    public static String trimToNull(String str)

    8、

    Removes control characters (char <= 32) from both

    ends of this String returning an empty String ("") if the String
    is empty ("") after the trim or if it is null.

    The String is trimmed using {@link String#trim()}.

    Trim removes start and end characters <= 32.
    To strip whitespace use {@link /stripToEmpty(String)}.

    格式化一个字符串中的空格，有非空判断处理，如果为空返回""； StringUtils.trimToEmpty(null) = "" StringUtils.trimToEmpty("") = "" StringUtils.trimToEmpty(" ") = "" StringUtils.trimToEmpty("abc") = "abc" StringUtils.trimToEmpty(" abc ") = "abc"

    @param str the String to be trimmed, may be null
    @return the trimmed String, or an empty String if null input
    @since 2.0
    public static String trimToEmpty(String str)

五、 字符串比较:
    9、
    Compares two Strings, returning true if they are equal.

    nulls are handled without exceptions. Two null

    references are considered to be equal. The comparison is case sensitive.

    判断两个字符串是否相等，有非空处理。 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

    @param str1 the first String, may be null
    @param str2 the second String, may be null
    @return true if the Strings are equal, case sensitive, or
    both null
    @see java.lang.String#equals(Object)
    public static boolean equals(String str1, String str2)

    10、

    Compares two Strings, returning true if they are equal ignoring

    the case.

    nulls are handled without exceptions. Two null

    references are considered equal. Comparison is case insensitive.

    判断两个字符串是否相等，有非空处理。忽略大小写 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

    @param str1 the first String, may be null
    @param str2 the second String, may be null
    @return true if the Strings are equal, case insensitive, or
    both null
    @see java.lang.String#equalsIgnoreCase(String)
    public static boolean equalsIgnoreCase(String str1, String str2)

    六、 IndexOf 处理
    11、

    Finds the first index within a String, handling null.

    This method uses {@link String#indexOf(String)}.

    A null String will return -1.

    返回要查找的字符串所在位置，有非空处理 StringUtils.indexOf(null, *) = -1 StringUtils.indexOf(*, null) = -1 StringUtils.indexOf("", "") = 0 StringUtils.indexOf("aabaabaa", "a") = 0 StringUtils.indexOf("aabaabaa", "b") = 2 StringUtils.indexOf("aabaabaa", "ab") = 1 StringUtils.indexOf("aabaabaa", "") = 0

    @param str the String to check, may be null
    @param searchStr the String to find, may be null
    @return the first index of the search String,
    -1 if no match or null string input
    @since 2.0
    public static int indexOf(String str, String searchStr)

    12、

    Finds the first index within a String, handling null.

    This method uses {@link String#indexOf(String, int)}.

    A null String will return -1.

    A negative start position is treated as zero.
    An empty ("") search String always matches.
    A start position greater than the string length only matches
    an empty search String.

    返回要由指定位置开始查找的字符串所在位置，有非空处理 StringUtils.indexOf(null, *, *) = -1 StringUtils.indexOf(*, null, *) = -1 StringUtils.indexOf("", "", 0) = 0 StringUtils.indexOf("aabaabaa", "a", 0) = 0 StringUtils.indexOf("aabaabaa", "b", 0) = 2 StringUtils.indexOf("aabaabaa", "ab", 0) = 1 StringUtils.indexOf("aabaabaa", "b", 3) = 5 StringUtils.indexOf("aabaabaa", "b", 9) = -1 StringUtils.indexOf("aabaabaa", "b", -1) = 2 StringUtils.indexOf("aabaabaa", "", 2) = 2 StringUtils.indexOf("abc", "", 9) = 3

    @param str the String to check, may be null
    @param searchStr the String to find, may be null
    @param startPos the start position, negative treated as zero
    @return the first index of the search String,
    -1 if no match or null string input
    @since 2.0
    public static int indexOf(String str, String searchStr, int startPos)

    七、 子字符串处理：
    13、
    Gets a substring from the specified String avoiding exceptions.

    A negative start position can be used to start n

    characters from the end of the String.

    A null String will return null.

    An empty ("") String will return "".

    返回指定位置开始的字符串中的所有字符 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"

    @param str the String to get the substring from, may be null
    @param start the position to start from, negative means
    count back from the end of the String by this many characters
    @return substring from start position, null if null String input
    public static String substring(String str, int start)

    14、

    Gets a substring from the specified String avoiding exceptions.

    A negative start position can be used to start/end n

    characters from the end of the String.

    The returned substring starts with the character in the start

    position and ends before the end position. All postion counting is
    zero-based -- i.e., to start at the beginning of the string use
    start = 0. Negative start and end positions can be used to
    specify offsets relative to the end of the String.

    If start is not strictly to the left of end, ""

    is returned.

    返回由开始位置到结束位置之间的子字符串 StringUtils.substring(null, *, *) = null StringUtils.substring("", * , *) = ""; StringUtils.substring("abc", 0, 2) = "ab" StringUtils.substring("abc", 2, 0) = "" StringUtils.substring("abc", 2, 4) = "c" StringUtils.substring("abc", 4, 6) = "" StringUtils.substring("abc", 2, 2) = "" StringUtils.substring("abc", -2, -1) = "b" StringUtils.substring("abc", -4, 2) = "ab"

    @param str the String to get the substring from, may be null
    @param start the position to start from, negative means
    count back from the end of the String by this many characters
    @param end the position to end at (exclusive), negative means
    count back from the end of the String by this many characters
    @return substring from start position to end positon,
    null if null String input
    public static String substring(String str, int start, int end)

    15、 SubStringAfter/SubStringBefore（前后子字符串处理：

    Gets the substring before the first occurance of a separator.

    The separator is not returned.

    A null string input will return null.

    An empty ("") string input will return the empty string.
    A null separator will return the input string.

返回指定字符串之前的所有字符 StringUtils.substringBefore(null, *) = null StringUtils.substringBefore("", *) = "" StringUtils.substringBefore("abc", "a") = "" StringUtils.substringBefore("abcba", "b") = "a" StringUtils.substringBefore("abc", "c") = "ab" StringUtils.substringBefore("abc", "d") = "abc" StringUtils.substringBefore("abc", "") = "" StringUtils.substringBefore("abc", null) = "abc"

    @param str the String to get a substring from, may be null
    @param separator the String to search for, may be null
    @return the substring before the first occurance of the separator,
    null if null String input
    @since 2.0
    public static String substringBefore(String str, String separator)

    16、

    Gets the substring after the first occurance of a separator.

    The separator is not returned.

    A null string input will return null.

    An empty ("") string input will return the empty string.
    A null separator will return the empty string if the
    input string is not null.

    返回指定字符串之后的所有字符 StringUtils.substringAfter(null, *) = null StringUtils.substringAfter("", *) = "" StringUtils.substringAfter(*, null) = "" StringUtils.substringAfter("abc", "a") = "bc" StringUtils.substringAfter("abcba", "b") = "cba" StringUtils.substringAfter("abc", "c") = "" StringUtils.substringAfter("abc", "d") = "" StringUtils.substringAfter("abc", "") = "abc"

    @param str the String to get a substring from, may be null
    @param separator the String to search for, may be null
    @return the substring after the first occurance of the separator,
    null if null String input
    @since 2.0
    public static String substringAfter(String str, String separator)

    17、

    Gets the substring before the last occurance of a separator.

    The separator is not returned.

    A null string input will return null.

    An empty ("") string input will return the empty string.
    An empty or null separator will return the input string.

    返回最后一个指定字符串之前的所有字符 StringUtils.substringBeforeLast(null, *) = null StringUtils.substringBeforeLast("", *) = "" StringUtils.substringBeforeLast("abcba", "b") = "abc" StringUtils.substringBeforeLast("abc", "c") = "ab" StringUtils.substringBeforeLast("a", "a") = "" StringUtils.substringBeforeLast("a", "z") = "a" StringUtils.substringBeforeLast("a", null) = "a" StringUtils.substringBeforeLast("a", "") = "a"

    @param str the String to get a substring from, may be null
    @param separator the String to search for, may be null
    @return the substring before the last occurance of the separator,
    null if null String input
    @since 2.0
    public static String substringBeforeLast(String str, String separator)

    18、

    Gets the substring after the last occurance of a separator.

    The separator is not returned.

    A null string input will return null.

    An empty ("") string input will return the empty string.
    An empty or null separator will return the empty string if
    the input string is not null.

    返回最后一个指定字符串之后的所有字符 StringUtils.substringAfterLast(null, *) = null StringUtils.substringAfterLast("", *) = "" StringUtils.substringAfterLast(*, "") = "" StringUtils.substringAfterLast(*, null) = "" StringUtils.substringAfterLast("abc", "a") = "bc" StringUtils.substringAfterLast("abcba", "b") = "a" StringUtils.substringAfterLast("abc", "c") = "" StringUtils.substringAfterLast("a", "a") = "" StringUtils.substringAfterLast("a", "z") = ""

    @param str the String to get a substring from, may be null
    @param separator the String to search for, may be null
    @return the substring after the last occurance of the separator,
    null if null String input
    @since 2.0
    public static String substringAfterLast(String str, String separator)

    八、 Replacing（字符串替换）
    19、
    Replaces all occurances of a String within another String.

    A null reference passed to this method is a no-op.

    以指定字符串替换原来字符串的的指定字符串 StringUtils.replace(null, *, *) = null StringUtils.replace("", *, *) = "" StringUtils.replace("aba", null, null) = "aba" StringUtils.replace("aba", null, null) = "aba" StringUtils.replace("aba", "a", null) = "aba" StringUtils.replace("aba", "a", "") = "aba" StringUtils.replace("aba", "a", "z") = "zbz"

    @param text text to search and replace in, may be null
    @param repl the String to search for, may be null
    @param with the String to replace with, may be null
    @return the text with any replacements processed,
    null if null String input
    @see #replace(String text, String repl, String with, int max)
    public static String replace(String text, String repl, String with)

    20、

    Replaces a String with another String inside a larger String,

    for the first max values of the search String.

    A null reference passed to this method is a no-op.

    以指定字符串最大替换原来字符串的的指定字符串 StringUtils.replace(null, *, *, *) = null StringUtils.replace("", *, *, *) = "" StringUtils.replace("abaa", null, null, 1) = "abaa" StringUtils.replace("abaa", null, null, 1) = "abaa" StringUtils.replace("abaa", "a", null, 1) = "abaa" StringUtils.replace("abaa", "a", "", 1) = "abaa" StringUtils.replace("abaa", "a", "z", 0) = "abaa" StringUtils.replace("abaa", "a", "z", 1) = "zbaa" StringUtils.replace("abaa", "a", "z", 2) = "zbza" StringUtils.replace("abaa", "a", "z", -1) = "zbzz"

    @param text text to search and replace in, may be null
    @param repl the String to search for, may be null
    @param with the String to replace with, may be null
    @param max maximum number of values to replace, or -1 if no maximum
    @return the text with any replacements processed,
    null if null String input
    public static String replace(String text, String repl, String with, int max)

    九、 Case conversion（大小写转换）
    21、

    Converts a String to upper case as per {@link String#toUpperCase()}.

    A null input String returns null.

    将一个字符串变为大写 StringUtils.upperCase(null) = null StringUtils.upperCase("") = "" StringUtils.upperCase("aBc") = "ABC"

    @param str the String to upper case, may be null
    @return the upper cased String, null if null String input
    public static String upperCase(String str) 22、

    Converts a String to lower case as per {@link String#toLowerCase()}.

    A null input String returns null.

    将一个字符串转换为小写 StringUtils.lowerCase(null) = null StringUtils.lowerCase("") = "" StringUtils.lowerCase("aBc") = "abc"

    @param str the String to lower case, may be null
    @return the lower cased String, null if null String input
    public static String lowerCase(String str) 23、

    Capitalizes a String changing the first letter to title case as

    per {@link Character#toTitleCase(char)}. No other letters are changed.

    For a word based alorithm, see {@link /WordUtils#capitalize(String)}.

    A null input String returns null.

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

    @param str the String to capitalize, may be null
    @return the capitalized String, null if null String input
    @see /WordUtils#capitalize(String)
    @see /uncapitalize(String)
    @since 2.0
    将字符串中的首字母大写
    public static String capitalize(String str)