Lombok

Annotation	Code	Result
Getter & Setter	public class User { @Getter private BigInteger id; @Setter private String username; private String password; private String email; }
ToString	@ToString public class User { private BigInteger id; private String username; private String password; private String email; }	// in target/classes/User.class public String toString() { return "User(id=" + this.getId() + ", username=" + this.getUsername() + ", password=" + this.getPassword() + ", email=" + this.getEmail() + ")"; }
EqualsAndHashCode
NonNull	//before class variables @NonNull private BigDecimal id; //before method arguments public void test(@NonNull String s) {...}	Performs null check
NoArgsConstructor	@NoArgsConstructor public class User { @NonNull private BigInteger id; private String username; private String password; private String email; }	public User() { }
RequiredArgsConstructor	@RequiredArgsConstructor public class User { @NonNull private BigInteger id; final private String username; private String password; private String email; }	// the arguments are NonNull and final variables public User(@NonNull BigInteger id, String username) { if (id == null) { throw new NullPointerException("id is marked non-null but is null"); } else { this.id = id; this.username = username; } }
AllArgsConstructor	@AllArgsConstructor public class User { @NonNull private BigInteger id; private String username; private String password; private String email; }	public User(@NonNull BigInteger id, String username, String password, String email) { if (id == null) { throw new NullPointerException("id is marked non-null but is null"); } else { this.id = id; this.username = username; this.password = password; this.email = email; } }
Data	@Data public class User { @NonNull private BigInteger id; final private String username; private String password; private String email; }	work as a combination of getter/setter, equalsAndHashcode, toString, requiredArgsConstructors.
Builder	@Data @Builder public class User { @NonNull private BigInteger id; final private String username; private String password; private String email; }
Log	@Log log.info("create user");
val	val map = new HashMap<String, String>();	work as val in JavaScript
CleanUp	@Cleanup InputStream in = null; @Cleanup FileOutputStream out = null;	Object in = null; try { FileOutputStream out = null; if (Collections.singletonList(out).get(0) != null) { ((FileOutputStream)out).close(); } } finally { if (Collections.singletonList(in).get(0) != null) { ((InputStream)in).close(); } }

Getter and Setter

1. AccessLevel

   The default Getter is public unless it is specified with an AccessLevel.

   @Getter(AccessLevel.MODULE)
   @Getter(AccessLevel.PACKAGE)
   @Getter(AccessLevel.PRIVATE)
   @Getter(AccessLevel.PROTECTED)
   @Getter(AccessLevel.PUBLIC)
   @Getter(AccessLevel.NONE) // will not generate getter & setter

2. lazy

   With lazy, the first time the getter is called, it will cache the value from then on.

   @Getter(lazy = true)

3. Getter and Setter can be added before the field or before the class

ToString

1. @ToString.Exclude:

   @ToString
   public class User {
       private BigInteger id;
       private String username;
       private String password;
       // skip email in toString()
       @ToString.Exclude private String email;
   }

2. @ToString.Include

3. callSuper = true will include the output of toString of superclass

   @ToString(callSuper = true)
   public class VipUser extends User{
       private boolean vipStatus;
   }
   
   // VipUser.toString()
   public String toString() {
       return "VipUser(super=" + super.toString() + ", vipStatus=" + this.vipStatus + ")";
   }

EqualsAndHashCode

• Code:

  @EqualsAndHashCode
  public class User {
      private BigInteger id;
      private String username;
      private String password;
      private String email;
  }

• Results:

  lombok will generate canEqual, equals, hashCode

  // in target/classes/User.class
  public boolean equals(Object o) {
      if (o == this) {
          return true;
      } else if (!(o instanceof User)) {
          return false;
      } else {
          User other = (User)o;
          if (!other.canEqual(this)) {
              return false;
          } else {
              label59: {
                  Object this$id = this.id;
                  Object other$id = other.id;
                  if (this$id == null) {
                      if (other$id == null) {
                          break label59;
                      }
                  } else if (this$id.equals(other$id)) {
                      break label59;
                  }
  
                  return false;
              }
  
              Object this$username = this.username;
              Object other$username = other.username;
              if (this$username == null) {
                  if (other$username != null) {
                      return false;
                  }
              } else if (!this$username.equals(other$username)) {
                  return false;
              }
  
              Object this$password = this.password;
              Object other$password = other.password;
              if (this$password == null) {
                  if (other$password != null) {
                      return false;
                  }
              } else if (!this$password.equals(other$password)) {
                  return false;
              }
  
              Object this$email = this.email;
              Object other$email = other.email;
              if (this$email == null) {
                  if (other$email != null) {
                      return false;
                  }
              } else if (!this$email.equals(other$email)) {
                  return false;
              }
  
              return true;
          }
      }
  }
  
  protected boolean canEqual(Object other) {
      return other instanceof User;
  }
  
  public int hashCode() {
      int PRIME = true;
      int result = 1;
      Object $id = this.id;
      int result = result * 59 + ($id == null ? 43 : $id.hashCode());
      Object $username = this.username;
      result = result * 59 + ($username == null ? 43 : $username.hashCode());
      Object $password = this.password;
      result = result * 59 + ($password == null ? 43 : $password.hashCode());
      Object $email = this.email;
      result = result * 59 + ($email == null ? 43 : $email.hashCode());
      return result;
  }

• exclude in EqualsAndHashCode

  @EqualsAndHashCode(exclude = {"password"})