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This article mainly introduces StringUtils and CollectionUtils to judge the empty method which is faster, the article is very detailed, has a certain reference value, interested friends must read it!

Conclusion

It is efficient to write and judge directly (usually 0ms), but the package is simple and rigorous (usually within 10ms).

The function StringUtils.isNotBlank (testString) is the opposite of StringUtils.isBlank (testString).

The function StringUtils.isNotEmpty (testString) is the opposite of StringUtils.isEmpty (testString).

The difference between isBlank and isEmpty

If the string is String str = "; / / or str ="

So if you judge it to be empty, you'd better use it.

StringUtils.isBlank (str) or stringent null &! ".equals (str.trim ())

CollectionUtils wrapper class, the method List list = new ArrayList (); CollectionUtils.isEmpty (list); Map map = new HashMap (); CollectionUtils.isEmpty (map)

Source code:

Public static boolean isEmpty (Collection collection) {return collection = = null | | collection.isEmpty ();} public static boolean isEmpty (Map map) {return map = = null | | map.isEmpty ();} / * Returns true if this list contains no elements. * * @ return true if this list contains no elements * / public boolean isEmpty () {return size = = 0;} / * Returns true if this map contains no key-value mappings. * * @ return true if this map contains no key-value mappings * / public boolean isEmpty () {return size = = 0;}

In view of the above methods, I think string judgment is empty StringUtils.isBlank (str).

Judge the collection or use the original code list! = null & & list.size > 0

Common methods of StringUtils and CollectionUtils tool classes

The following will show you the common methods of StringUtils and CollectionUtils tool classes.

1. CollectionUtils tool class

Function: often used to determine whether there are elements in the collection, whether it is empty, etc.

★★★ example 1: determine whether the collection is empty: CollectionUtils.isEmpty (null); / console print: true CollectionUtils.isEmpty (new ArrayList ()); / / console print: true CollectionUtils.isEmpty ({azob}); / / console print: false ★★★ example 2: determine whether the collection is not empty: CollectionUtils.isNotEmpty (null); / / console print: false CollectionUtils.isNotEmpty (new ArrayList ()) / / console print: false CollectionUtils.isNotEmpty ({arecom b}); / / console print: true1, work case

1.1. Database user entity

Public class User implements Serializable {private Long id; / / user ID private String name; / / user name private Integer age; / / user age.}

1.2 、 Mapper

/ * the editor (program Niu CodeCow) writes sql with annotations, or sql with XML. See personal hobbies * / @ Select ("" + "select * from User" + ") List getUserList (); / / get all users

1.3, testing

@ Autowiredprivate UserMapper userMapper;List list = userMapper.getUserList (); / / call the Mapper method to get all users if (CollectionUtils.isEmpty (list)) {/ / use the CollectionUtils tool to determine whether it is empty / / the business logic operations that are empty here} else {/ / the business logic operations that are not empty here} II. StringUtils tool class

1. Function: it is often used to judge whether the string is empty, "", null, etc.

★★★ example 1: judge whether a string is empty (empty standard: string is null or string length is 0) StringUtils.isEmpty (null); / / console print: true StringUtils.isEmpty (""); / / console print: true StringUtils.isEmpty ("") / / console print: false (non-empty space in StringUtils) StringUtils.isEmpty ("program cow CodeCow") / / console print: false ★★★ example 2: determine whether a string is empty (as opposed to example 1) StringUtils.isNotEmpty (null); / / console print: false StringUtils.isNotEmpty ("); / / console print: false StringUtils.isNotEmpty (") / / console print: true StringUtils.isNotEmpty ("program cow CodeCow"); / / console print: true ★★★ example 3: determine whether a string is empty StringUtils.isBlank (null); / / console print: true StringUtils.isBlank ("); / / console print: true StringUtils.isBlank (") / / console print: true StringUtils.isBlank ("program cow CodeCow") / / console print: false ★★★ example 4: determine whether a string is empty (contrary to example 3) StringUtils.isNotBlank (null); / / console print: false StringUtils.isNotBlank ("); / console print: false StringUtils.isNotBlank (") / / console print: false StringUtils.isBlank ("program cow CodeCow") / / console print: true ☆ isEmpty, isBlank are used to determine whether the string is empty, what's the difference between them? Just remember one thing: isBlank can be said to be more stringent, for example: isBlank (") isBlank says my TM says it is" empty "isEmpty (") isEmpty says my TM says it is" not empty ", do you understand ^ _ ^ 2, work case

2.1. Guide the package first

/ / Import commons package; editor (program Niu CodeCow) uses lang3. Org.apache.commons commons-lang3 3.9 is recommended.

2.2, testing

1 "the test editor (CodeCow) does not have much BB. If you take a closer look at the above, you should know how to do it ^ _ ^"

The above is all the contents of the article "which method is faster for StringUtils or CollectionUtils to judge empty". Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

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