Gangmax Blog

Lombok

Lombok is a Java library which provides a set of annotations with which you can simplify your Java code(get rid of “getter/setter/equals/hashcode” and etc) by using the annotations, after that Lombok will generate the boilerplate code for you during the compiling/building time(“compile” for “Eclipse/IntelliJ IDEA with plugins”, “build” for “Maven/Gradle”) with the annotation information. Then you can use the Java classes as vanilla Java classes.

An example tells everything:

With Lombok
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import lombok.AccessLevel;
import lombok.Setter;
import lombok.Data;
import lombok.ToString;

@Data public class DataExample {
private final String name;
@Setter(AccessLevel.PACKAGE) private int age;
private double score;
private String[] tags;

@ToString(includeFieldNames=true)
@Data(staticConstructor="of")
public static class Exercise<T> {
private final String name;
private final T value;
}
}
Without Lombok
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import java.util.Arrays;

public class DataExample {
private final String name;
private int age;
private double score;
private String[] tags;

public DataExample(String name) {
this.name = name;
}

public String getName() {
return this.name;
}

void setAge(int age) {
this.age = age;
}

public int getAge() {
return this.age;
}

public void setScore(double score) {
this.score = score;
}

public double getScore() {
return this.score;
}

public String[] getTags() {
return this.tags;
}

public void setTags(String[] tags) {
this.tags = tags;
}

@Override public String toString() {
return "DataExample(" + this.getName() + ", " + this.getAge() + ", " + this.getScore() + ", " + Arrays.deepToString(this.getTags()) + ")";
}

protected boolean canEqual(Object other) {
return other instanceof DataExample;
}

@Override public boolean equals(Object o) {
if (o == this) return true;
if (!(o instanceof DataExample)) return false;
DataExample other = (DataExample) o;
if (!other.canEqual((Object)this)) return false;
if (this.getName() == null ? other.getName() != null : !this.getName().equals(other.getName())) return false;
if (this.getAge() != other.getAge()) return false;
if (Double.compare(this.getScore(), other.getScore()) != 0) return false;
if (!Arrays.deepEquals(this.getTags(), other.getTags())) return false;
return true;
}

@Override public int hashCode() {
final int PRIME = 59;
int result = 1;
final long temp1 = Double.doubleToLongBits(this.getScore());
result = (result*PRIME) + (this.getName() == null ? 43 : this.getName().hashCode());
result = (result*PRIME) + this.getAge();
result = (result*PRIME) + (int)(temp1 ^ (temp1 >>> 32));
result = (result*PRIME) + Arrays.deepHashCode(this.getTags());
return result;
}

public static class Exercise<T> {
private final String name;
private final T value;

private Exercise(String name, T value) {
this.name = name;
this.value = value;
}

public static <T> Exercise<T> of(String name, T value) {
return new Exercise<T>(name, value);
}

public String getName() {
return this.name;
}

public T getValue() {
return this.value;
}

@Override public String toString() {
return "Exercise(name=" + this.getName() + ", value=" + this.getValue() + ")";
}

protected boolean canEqual(Object other) {
return other instanceof Exercise;
}

@Override public boolean equals(Object o) {
if (o == this) return true;
if (!(o instanceof Exercise)) return false;
Exercise<?> other = (Exercise<?>) o;
if (!other.canEqual((Object)this)) return false;
if (this.getName() == null ? other.getValue() != null : !this.getName().equals(other.getName())) return false;
if (this.getValue() == null ? other.getValue() != null : !this.getValue().equals(other.getValue())) return false;
return true;
}

@Override public int hashCode() {
final int PRIME = 59;
int result = 1;
result = (result*PRIME) + (this.getName() == null ? 43 : this.getName().hashCode());
result = (result*PRIME) + (this.getValue() == null ? 43 : this.getValue().hashCode());
return result;
}
}
}

Reference:

  1. How to use Lombok with IDEs/Maven/Gradle/…

  2. Reducing Boilerplate Code with Project Lombok

  3. Lombok source code

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