LomBok 的相关目录已经整理出来,希望大家可以根据需求自助学习,好工具要大家分享:
实现equals, hashCode方法是在编程生活中再常见不过的一个东西了,那么自然@EqualsAndHashCode 这个annotation就成为了一个非常方便的工具。默认情况下,被这个annotation标注的class会用到除了 static,transient修饰的所有属性作为判断标准,当然和之前的annotation一样,可是使用exclude选项除掉不想要的属性。也可以通过callSuper包含父类的equals 和 hashCode。 当然如果你的class 没有继承任何其他的class,你却写了callSuper,那么会收获一个编译报错。
你只要这样用:
import lombok.EqualsAndHashCode; @EqualsAndHashCode(exclude={"id", "shape"}) public class EqualsAndHashCodeExample { private transient int transientVar = 10; private String name; private double score; private Shape shape = new Square(5, 10); private String[] tags; private int id; public String getName() { return this.name; } @EqualsAndHashCode(callSuper=true) public static class Square extends Shape { private final int width, height; public Square(int width, int height) { this.width = width; this.height = height; } } }
就可以得到这样的效果:
import java.util.Arrays; public class EqualsAndHashCodeExample { private transient int transientVar = 10; private String name; private double score; private Shape shape = new Square(5, 10); private String[] tags; private int id; public String getName() { return this.name; } @Override public boolean equals(Object o) { if (o == this) return true; if (!(o instanceof EqualsAndHashCodeExample)) return false; EqualsAndHashCodeExample other = (EqualsAndHashCodeExample) o; if (!other.canEqual((Object)this)) return false; if (this.getName() == null ? other.getName() != null : !this.getName().equals(other.getName())) return false; if (Double.compare(this.score, other.score) != 0) return false; if (!Arrays.deepEquals(this.tags, other.tags)) return false; return true; } @Override public int hashCode() { final int PRIME = 59; int result = 1; final long temp1 = Double.doubleToLongBits(this.score); result = (result*PRIME) + (this.name == null ? 0 : this.name.hashCode()); result = (result*PRIME) + (int)(temp1 ^ (temp1 >>> 32)); result = (result*PRIME) + Arrays.deepHashCode(this.tags); return result; } protected boolean canEqual(Object other) { return other instanceof EqualsAndHashCodeExample; } public static class Square extends Shape { private final int width, height; public Square(int width, int height) { this.width = width; this.height = height; } @Override public boolean equals(Object o) { if (o == this) return true; if (!(o instanceof Square)) return false; Square other = (Square) o; if (!other.canEqual((Object)this)) return false; if (!super.equals(o)) return false; if (this.width != other.width) return false; if (this.height != other.height) return false; return true; } @Override public int hashCode() { final int PRIME = 59; int result = 1; result = (result*PRIME) + super.hashCode(); result = (result*PRIME) + this.width; result = (result*PRIME) + this.height; return result; } protected boolean canEqual(Object other) { return other instanceof Square; } } }
这就是Lombok的优势所在。几个需要注意的点是,对于Array类型的变量,如果需要进行equals和hashCode的时候需要调用工具类的Arrays中的deepHashCode, deepEquals完成比较。