The article directories

• 1. What is Lombok
• 2. Lombok principle
• 3. Lombok uses annotations
• • 1. @getter and @setter methods
  • 2. @ ToString method
  • 3. @EqualsAndHashCode
  • 4. @NonNull
  • @noargsconstructor and @requiredargsconstructor and @allargsconstructor
  • 6. @Data
  • 7. @Builder
  • 8. @Log
  • 9. val
  • 10. @Cleanup
• 4. To summarize

1. What is Lombok

• Liverpoolfc.tv: projectlombok.org/
• Project Lombok is a java library that automatically plugs into your editor and build tools, spicing up your java. Never write another getter or equals method again, with one annotation your class has a fully featured builder, Automate your logging variables, and much more.
• In plain English: Lombok is a Java™ utility that helps developers eliminate verbose code in Java, especially for simple onesJava Objects (POJOs)It does this through annotations.
• To simplify theJavaBeanThe development of

<dependency>
	<groupId>org.projectlombok</groupId>
	<artifactId>lombok</artifactId>
</dependency>
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• Idea search for installationlombokThe plug-in
  
  
• Lombok @Dataannotations
• According to the shortcut keyAlt+7Displays all the methods in the current class, global constants, and methods including parameters and return values
• Or View – >Tool Windows – >Structure – > click

2. Lombok principle

3. Lombok uses annotations

1. @getter and @setter methods

2. @ ToString method

• Customize ToString methods that exclude certain fields
  
  
  
  

3. @EqualsAndHashCode

4. @NonNull

• Purpose: The purpose of the annotation is to make a non-null judgment in the method
• Case study:

public void test(@NonNull String s){
        System.out.println(s);
}
public static void main(String[] args) {
        User user = new User();
        user.test(null);
    }
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• Result: null pointer
  
  
• View the compiled source code:

public void test(@NonNull String s) {
        if (s == null) {
            throw new NullPointerException("s is marked non-null but is null");
        } else{ System.out.println(s); }}Copy the code

• You can also use it in constructors, or you can add annotations to fields

@NotNull private Integer id;
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@noargsconstructor and @requiredargsconstructor and @allargsconstructor

6. @Data

• Applied to a class, it is a collection of annotations: @toString, @equalSandHashCode, @getter, @setter @requiredargsConstructor

7. @Builder

8. @Log

• @log: applied to a class to generate a Log variable. There are different annotations for different logging implementations:

9. val

HashMap<String,String> map = new HashMap<String,String>();
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val map = new HashMap<String,String>();
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public static void main(String[] args) {
    val sets = new HashSet<String>();
    val lists = new ArrayList<String>();
    val maps = new HashMap<String, String>();
    //=> Equivalent to the following
    final Set<String> sets2 = new HashSet<>();
    final List<String> lists2 = new ArrayList<>();
    final Map<String, String> maps2 = new HashMap<>();
}
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10. @Cleanup

• Used to close and release resources that can be used on IO streams;

public class CleanupExample {
    public static void main(String[] args) throws IOException {
        @Cleanup InputStream in = new FileInputStream(args[0]);
        @Cleanup OutputStream out = new FileOutputStream(args[1]);
        byte[] b = new byte[10000];
        while (true) {
            int r = in.read(b);
            if (r == -1) break;
            out.write(b, 0, r); }}}Copy the code

• The above is equivalent to traditional Java code like this:

public class CleanupExample {
  public static void main(String[] args) throws IOException {
    InputStream in = new FileInputStream(args[0]);
    try {
      OutputStream out = new FileOutputStream(args[1]);
      try {
        byte[] b = new byte[10000];
        while (true) {
          int r = in.read(b);
          if (r == -1) break;
          out.write(b, 0, r); }}finally {
        if(out ! =null) { out.close(); }}}finally {
      if(in ! =null) { in.close(); }}}}Copy the code

4. To summarize