isEmpty 和 isBlank 的用法区别，至少一半的人答不上来...
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大家好，我是程序汪，开发中经常有些小细节容易忽略，这些小细节往往容易导致代码缺陷，今天分享一波工具类的小细节
也许你两个都不知道,也许你除了isEmpty/isNotEmpty/isNotBlank/isBlank外,并不知道还有isAnyEmpty/isNoneEmpty/isAnyBlank/isNoneBlank的存在, come on ,让我们一起来探索org.apache.commons.lang3.StringUtils;这个工具类。
isEmpty系列
StringUtils.isEmpty()
是否为空. 可以看到 " " 空格是会绕过这种空判断,因为是一个空格,并不是严格的空值,会导致 isEmpty(" ")=false
StringUtils.isEmpty(null) = true
StringUtils.isEmpty("") = true
StringUtils.isEmpty(" ") = false
StringUtils.isEmpty("bob") = false
StringUtils.isEmpty(" bob ") = false
/**
*
* <p>NOTE: This method changed in Lang version 2.0.
* It no longer trims the CharSequence.
* That functionality is available in isBlank().</p>
*
* @param cs the CharSequence to check, may be null
* @return {@code true} if the CharSequence is empty or null
* @since 3.0 Changed signature from isEmpty(String) to isEmpty(CharSequence)
*/
public static boolean isEmpty(final CharSequence cs) {
return cs == null || cs.length() == 0;
}
StringUtils.isNotEmpty()
相当于不为空 , = !isEmpty()。
public static boolean isNotEmpty(final CharSequence cs) {
return !isEmpty(cs);
}
StringUtils.isAnyEmpty()
是否有一个为空,只有一个为空,就为true。
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
/**
* @param css the CharSequences to check, may be null or empty
* @return {@code true} if any of the CharSequences are empty or null
* @since 3.2
*/
public static boolean isAnyEmpty(final CharSequence... css) {
if (ArrayUtils.isEmpty(css)) {
return true;
}
for (final CharSequence cs : css){
if (isEmpty(cs)) {
return true;
}
}
return false;
}
StringUtils.isNoneEmpty()
相当于!isAnyEmpty(css) , 必须所有的值都不为空才返回true
/**
* <p>Checks if none of the CharSequences are empty ("") or null.</p>
*
* <pre>
* 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
* </pre>
*
* @param css the CharSequences to check, may be null or empty
* @return {@code true} if none of the CharSequences are empty or null
* @since 3.2
*/
public static boolean isNoneEmpty(final CharSequence... css) {
isBank系列
StringUtils.isBlank()
是否为真空值(空格或者空值)
StringUtils.isBlank(null) = true
StringUtils.isBlank("") = true
StringUtils.isBlank(" ") = true
StringUtils.isBlank("bob") = false
StringUtils.isBlank(" bob ") = false
/**
* <p>Checks if a CharSequence is whitespace, empty ("") or null.</p>
* @param cs the CharSequence to check, may be null
* @return {@code true} if the CharSequence is null, empty or whitespace
* @since 2.0
* @since 3.0 Changed signature from isBlank(String) to isBlank(CharSequence)
*/
public static boolean isBlank(final CharSequence cs) {
int strLen;
if (cs == null || (strLen = cs.length()) == 0) {
return true;
}
for (int i = 0; i < strLen; i++) {
if (Character.isWhitespace(cs.charAt(i)) == false) {
return false;
}
}
return true;
}
StringUtils.isNotBlank()
是否真的不为空,不是空格或者空值 ,相当于!isBlank();
public static boolean isNotBlank(final CharSequence cs) {
return !isBlank(cs);
}
StringUtils.isAnyBlank()
是否包含任何真空值(包含空格或空值)
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
/**
* <p>Checks if any one of the CharSequences are blank ("") or null and not whitespace only..</p>
* @param css the CharSequences to check, may be null or empty
* @return {@code true} if any of the CharSequences are blank or null or whitespace only
* @since 3.2
*/
public static boolean isAnyBlank(final CharSequence... css) {
if (ArrayUtils.isEmpty(css)) {
return true;
}
for (final CharSequence cs : css){
if (isBlank(cs)) {
return true;
}
}
return false;
}
StringUtils.isNoneBlank()
是否全部都不包含空值或空格
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
/**
* <p>Checks if none of the CharSequences are blank ("") or null and whitespace only..</p>
* @param css the CharSequences to check, may be null or empty
* @return {@code true} if none of the CharSequences are blank or null or whitespace only
* @since 3.2
*/
public static boolean isNoneBlank(final CharSequence... css) {
return !isAnyBlank(css);
}
StringUtils的其他方法
可以参考官方的文档,里面有详细的描述,有些方法还是很好用的。
https://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/StringUtils.html
| 方法名 | 英文解释 | 中文解释 |
|---|---|---|
| IsEmpty/IsBlank | checks if a String contains text | 检查字符串是否包含文本 |
| Trim/Strip | removes leading and trailing whitespace | 删除前导和尾随空格 |
| Equals/Compare | compares two strings null-safe | 比较两个字符串是否为null安全的 |
| startsWith | check if a String starts with a prefix null-safe | 检查字符串是否以前缀null安全开头 |
| endsWith | check if a String ends with a suffix null-safe | 检查字符串是否以后缀null安全结尾 |
| IndexOf/LastIndexOf/Contains | null-safe index-of checks | 包含空安全索引检查 |
| IndexOfAny/LastIndexOfAny/IndexOfAnyBut/LastIndexOfAnyBut | index-of any of a set of Strings | 任意一组字符串的索引 |
| ContainsOnly/ContainsNone/ContainsAny | does String contains only/none/any of these characters | 字符串是否仅包含/无/这些字符中的任何一个 |
| Substring/Left/Right/Mid | null-safe substring extractions | 字符串安全提取 |
| SubstringBefore/SubstringAfter/SubstringBetween | substring extraction relative to other strings -相对其他字符串的字符串提取 | |
| Split/Join | splits a String into an array of substrings and vice versa | 将字符串拆分为子字符串数组，反之亦然 |
| Remove/Delete | removes part of a String -删除字符串的一部分 | |
| Replace/Overlay | Searches a String and replaces one String with another | 搜索字符串，然后用另一个字符串替换 |
| Chomp/Chop | removes the last part of a String | 删除字符串的最后一部分 |
| AppendIfMissing | appends a suffix to the end of the String if not present | 如果不存在后缀，则在字符串的末尾附加一个后缀 |
| PrependIfMissing | prepends a prefix to the start of the String if not present | 如果不存在前缀，则在字符串的开头添加前缀 |
| LeftPad/RightPad/Center/Repeat | pads a String | 填充字符串 |
| UpperCase/LowerCase/SwapCase/Capitalize/Uncapitalize | changes the case of a String | 更改字符串的大小写 |
| CountMatches | counts the number of occurrences of one String in another | 计算一个字符串在另一个字符串中出现的次数 |
| IsAlpha/IsNumeric/IsWhitespace/IsAsciiPrintable | checks the characters in a String | 检查字符串中的字符 |
| DefaultString | protects against a null input String | 防止输入字符串为空 |
| Rotate | rotate (circular shift) a String | 旋转（循环移位）字符串 |
| Reverse/ReverseDelimited | reverses a String -反转字符串 | |
| Abbreviate | abbreviates a string using ellipsis or another given String | 使用省略号或另一个给定的String缩写一个字符串 |
| Difference | compares Strings and reports on their differences | 比较字符串并报告其差异 |
| LevenshteinDistance | the number of changes needed to change one String into another | 将一个String转换为另一个String所需的更改次数 |
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