lombok使用基础教程

• 本文作者：@Ryan Miao
• 本文链接：https://www.cnblogs.com/woshimrf/p/lombok-usage.html
• 版权声明： 本博客所有文章除特别声明外，均采用 CC BY-NC-SA 3.0 许可协议。转载请注明出处！

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前言

lombok是一个编译级别的插件，它可以在项目编译的时候生成一些代码。在很多工具类的项目中都有这个功能。比如dagger。

通俗的说，lombok可以通过注解来标示生成getter settter等代码。我们自然可以通过编译器比如IDEA的Generate生成，为啥要用这个？

在项目开发阶段，一个class的属性是一直变化的，今天可能增加一个字段，明天可能删除一个字段。每次变化都需要修改对应的模板代码。另外，有的class的字段超级多，多到一眼看不完。如果加上模板代码，更难一眼看出来。更有甚者，由于字段太多，想要使用builder来创建。手动创建builder和字段和原来的类夹杂在一起，看起来真的难受。lombok的@Builder即可解决这个问题。

引入

引入就是加入lombok的jar包。

在maven中

直接加入依赖

<dependency> <groupId>org.projectlombok</groupId> <artifactId>lombok</artifactId> <version>1.16.20</version> </dependency>

在gradle中

这里比较麻烦，需要添加一个编译时生成代码的插件。gradle里有几个这样的插件。但为了简化过程，lombok提供了新插件。

来源：官网， github

首先，添加一个plugin

plugins { id 'io.franzbecker.gradle-lombok' version '1.11' }

然后，就可以了。还可以配置lombok的版本：

lombok { // optional: values below are the defaults version = "1.16.20" sha256 = "" }

IntelIJ IDEA 插件

在IDEA里使用需要添加一个插件。在插件里搜索lombok，安装，重启。

IDEA里需要在设置中启用annotation processors。

基本用法

测试代码： https://github.com/Ryan-Miao/someTest/tree/master/src/main/java/com/test/lombok

Geeter Setter

最简单的，最常用的，最直观的使用就是getter setter方法。

package com.test.lombok;

import lombok.AccessLevel;
import lombok.Getter;
import lombok.Setter;

import java.util.Date;

/**
 * Created by Ryan Miao on 1/18/18.
 */
public class GetterSetterExample {
    /**
     * Age of the person. Water is wet.
     *
     * @param age New value for this person's age. Sky is blue.
     * @return The current value of this person's age. Circles are round.
     */
    @Getter
    @Setter
    private int age = 10;

    @Getter
    @Setter
    private boolean active;

    @Getter
    @Setter
    private Boolean none;

    @Getter
    @Setter
    private Date date;

    /**
     * Name of the person.
     * -- SETTER --
     * Changes the name of this person.
     *
     * @param name The new value.
     */
    @Setter(AccessLevel.PROTECTED) private String name;

    @Override public String toString() {
        return String.format("%s (age: %d)", name, age);
    }

    public static void main(String[] args) {
        GetterSetterExample example = new GetterSetterExample();
        example.setActive(true);
        example.setAge(123);
        example.setDate(new Date());
        example.setName("abc");
        example.setNone(false);

        Date date = example.getDate();
        Boolean none = example.getNone();
        boolean active = example.isActive();
        
    }
}

简单使用没有问题，深入一点可以看到有些特殊设定。比如javadoc.

1. Getter声明创建getter方法；
2. Setter声明创建setter方法；
3. @Setter(AccessLevel.PROTECTED)可以添加参数，指定权限为私有；
4. Attention！关于boolean的set前缀都是set，但getter不同，小写的boolean，即基本类型，前缀是is; Boolean，即包装类型，前缀是get；

编译后的结果如下：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.test.lombok;

import java.util.Date;

public class GetterSetterExample {
    private int age = 10;
    private boolean active;
    private Boolean none;
    private Date date;
    private String name;

    public GetterSetterExample() {
    }

    public String toString() {
        return String.format("%s (age: %d)", this.name, this.age);
    }

    public static void main(String[] args) {
        GetterSetterExample example = new GetterSetterExample();
        example.setActive(true);
        example.setAge(123);
        example.setDate(new Date());
        example.setName("abc");
        example.setNone(false);
        Date date = example.getDate();
        Boolean none = example.getNone();
        boolean active = example.isActive();
    }

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

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

    public boolean isActive() {
        return this.active;
    }

    public void setActive(boolean active) {
        this.active = active;
    }

    public Boolean getNone() {
        return this.none;
    }

    public void setNone(Boolean none) {
        this.none = none;
    }

    public Date getDate() {
        return this.date;
    }

    public void setDate(Date date) {
        this.date = date;
    }

    protected void setName(String name) {
        this.name = name;
    }
}

 

ToString

虽然ToString在生产环境貌似没什么卵用。但是，很多情况下，我们还是需要这个的。因为记log。不想每次看log的时候是一串@地址，那就好好把toString()加上。

package com.test.lombok;

import lombok.Setter;
import lombok.ToString;


/**
 * Created by Ryan Miao on 1/18/18.
 */
@Setter
@ToString(exclude="id")
public class ToStringExample {
    private static final int STATIC_VAR = 10;
    private String name;
    private Shape shape = new Square(5, 10);
    private String[] tags;
    private int id;


    @ToString(callSuper=true, includeFieldNames=true)
    public static class Square extends Shape {
        private final int width, height;

        public Square(int width, int height) {
            this.width = width;
            this.height = height;
        }
    }

    @ToString
    public static class Shape {
        private int color;

    }

    public static void main(String[] args) {
        final ToStringExample example = new ToStringExample();
        example.setId(1);
        example.setName("abc");
        example.setTags(new String[]{"a","b","c"});

        final Shape shape = new Square(1,2);
        example.setShape(shape);

        System.out.println(example.toString());
    }
}

1.@ToString最简单使用即可

打印结果如下：

ToStringExample(name=abc, shape=ToStringExample.Square(super=ToStringExample.Shape(color=0), width=1, height=2), tags=[a, b, c])

编译后的代码如下：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.test.lombok;

import java.util.Arrays;

public class ToStringExample {
    private static final int STATIC_VAR = 10;
    private String name;
    private ToStringExample.Shape shape = new ToStringExample.Square(5, 10);
    private String[] tags;
    private int id;

    public ToStringExample() {
    }

    public static void main(String[] args) {
        ToStringExample example = new ToStringExample();
        example.setId(1);
        example.setName("abc");
        example.setTags(new String[]{"a", "b", "c"});
        ToStringExample.Shape shape = new ToStringExample.Square(1, 2);
        example.setShape(shape);
        System.out.println(example.toString());
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setShape(ToStringExample.Shape shape) {
        this.shape = shape;
    }

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

    public void setId(int id) {
        this.id = id;
    }

    public String toString() {
        return "ToStringExample(name=" + this.name + ", shape=" + this.shape + ", tags=" + Arrays.deepToString(this.tags) + ")";
    }

    public static class Shape {
        private int color;

        public Shape() {
        }

        public String toString() {
            return "ToStringExample.Shape(color=" + this.color + ")";
        }
    }

    public static class Square extends ToStringExample.Shape {
        private final int width;
        private final int height;

        public Square(int width, int height) {
            this.width = width;
            this.height = height;
        }

        public String toString() {
            return "ToStringExample.Square(super=" + super.toString() + ", width=" + this.width + ", height=" + this.height + ")";
        }
    }
}

@EqualsAndHashCode

equals()和hashCode()在Java中有着举足轻重的基地作用，虽然通常很少关注。但是，这个必须不可省。不知道有几个可以手写出来的。

package com.test.lombok;

import lombok.EqualsAndHashCode;

/**
 * Created by Ryan Miao on 1/18/18.
 */
@EqualsAndHashCode(exclude={"id", "shape"})
public class EqualsAndHashCodeExample {
    private transient int transientVar = 10;
    private String name;
    private double score;
    private ToStringExample.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 ToStringExample.Shape {
        private final int width, height;

        public Square(int width, int height) {
            this.width = width;
            this.height = height;
        }
    }

    public static void main(String[] args) {
        EqualsAndHashCodeExample example = new EqualsAndHashCodeExample();
        EqualsAndHashCodeExample example1 = new EqualsAndHashCodeExample();
        boolean equals = example.equals(example1);
        boolean b = example.canEqual(example);
        int i = example.hashCode();
    }
}

编译后的结果为：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.test.lombok;

import com.test.lombok.ToStringExample.Shape;
import java.util.Arrays;

public class EqualsAndHashCodeExample {
    private transient int transientVar = 10;
    private String name;
    private double score;
    private Shape shape = new EqualsAndHashCodeExample.Square(5, 10);
    private String[] tags;
    private int id;

    public EqualsAndHashCodeExample() {
    }

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

    public static void main(String[] args) {
        EqualsAndHashCodeExample example = new EqualsAndHashCodeExample();
        EqualsAndHashCodeExample example1 = new EqualsAndHashCodeExample();
        example.equals(example1);
        boolean b = example.canEqual(example);
        int i = example.hashCode();
    }

    public boolean equals(Object o) {
        if (o == this) {
            return true;
        } else if (!(o instanceof EqualsAndHashCodeExample)) {
            return false;
        } else {
            EqualsAndHashCodeExample other = (EqualsAndHashCodeExample)o;
            if (!other.canEqual(this)) {
                return false;
            } else {
                label31: {
                    Object this$name = this.getName();
                    Object other$name = other.getName();
                    if (this$name == null) {
                        if (other$name == null) {
                            break label31;
                        }
                    } else if (this$name.equals(other$name)) {
                        break label31;
                    }

                    return false;
                }

                if (Double.compare(this.score, other.score) != 0) {
                    return false;
                } else {
                    return Arrays.deepEquals(this.tags, other.tags);
                }
            }
        }
    }

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

    public int hashCode() {
        int PRIME = true;
        int result = 1;
        Object $name = this.getName();
        int result = result * 59 + ($name == null ? 43 : $name.hashCode());
        long $score = Double.doubleToLongBits(this.score);
        result = result * 59 + (int)($score >>> 32 ^ $score);
        result = result * 59 + Arrays.deepHashCode(this.tags);
        return result;
    }

    public static class Square extends Shape {
        private final int width;
        private final int height;

        public Square(int width, int height) {
            this.width = width;
            this.height = height;
        }

        public boolean equals(Object o) {
            if (o == this) {
                return true;
            } else if (!(o instanceof EqualsAndHashCodeExample.Square)) {
                return false;
            } else {
                EqualsAndHashCodeExample.Square other = (EqualsAndHashCodeExample.Square)o;
                if (!other.canEqual(this)) {
                    return false;
                } else if (!super.equals(o)) {
                    return false;
                } else if (this.width != other.width) {
                    return false;
                } else {
                    return this.height == other.height;
                }
            }
        }

        protected boolean canEqual(Object other) {
            return other instanceof EqualsAndHashCodeExample.Square;
        }

        public int hashCode() {
            int PRIME = true;
            int result = super.hashCode();
            result = result * 59 + this.width;
            result = result * 59 + this.height;
            return result;
        }
    }
}

构造函数@NoArgsConstructor, @RequiredArgsConstructor, @AllArgsConstructor

Java中class的一切起源于构造器。大家最喜欢的还是构造函数创建对象。这里有一点比较坑的是无参构造函数。当你自己添加一个带有参数的构造函数后，无参构造函数则别隐藏。通常也没啥问题，但当你使用jackson反序列化对象的时候就被恶心到了。jackson通过无参构造函数创建对象。因此，当你考虑这个class会用来序列化为json的时候，即必须手动添加一个无参数构造函数。

@NoArgsConstructor

当你想要创建一个valueobject，DDD中的值对象，要求实现Immutable，那么无参数构造器就不合适了。@NoArgsConstructor会生成一个空的构造器。如果你设置了final field，那么编译会报错。如果你强制执行创建无参数构造器。即，@NoArgsConstructor(force = true)，那么final的field会初始化为0/false/null。通常适合与@Data集成。

@NoArgsConstructor
public static class NoArgsExample {
    @NonNull private String field;
}

• NonNull被忽略了

最终生成代码如下：

public static class NoArgsExample {
    @NonNull
    private String field;

    public NoArgsExample() {
    }
}

对于final的字段，我认为我不会用空构造器来做这件事。所以，感觉这个参数force=true不要也罢，鸡肋。

@RequiredArgsConstructor

一个class可以有很多属性，但你可能只关心其中的几个字段，那么可以使用@RequiredArgsConstructor。@NonNull将标注这个字段不应为null，初始化的时候会检查是否为空，否则抛出NullPointException。在上面的无参构造函数中被忽略了。那么，对于关注的字段标注@NonNull, @RequiredArgsConstructor则会生成带有这些字段的构造器。

@RequiredArgsConstructor
public class RequiredArgsExample {
    @NonNull private String field;
    private Date date;
    private Integer integer;
    private int i;
    private boolean b;
    private Boolean aBoolean;
}

 

最终生成结果：

public class RequiredArgsExample {
    @NonNull
    private String field;
    private Date date;
    private Integer integer;
    private int i;
    private boolean b;
    private Boolean aBoolean;

    public RequiredArgsExample(@NonNull String field) {
        if (field == null) {
            throw new NullPointerException("field");
        } else {
            this.field = field;
        }
    }
}

只有@NonNull会生成构造器。其他默认，Java的class初始化默认为null.false,0.

lombok提供了另一种初始化做法，静态初始化。即私有构造器，使用静态方法创建对象。这种做法看起来简单，但通常用的不多。因为静态初始化的东西很难mock，对测试不够友好。

@RequiredArgsConstructor(staticName = "of")
public static class RequiredArgsStaticExample {
    @NonNull private String field;
    private Date date;
    private Integer integer;
    private int i;
    private boolean b;
    private Boolean aBoolean;
}

最终生成代码如下：

public class ConstructorExample<T> {
    private int x;
    private int y;
    @NonNull
    private T description;
    private ConstructorExample(@NonNull T description) {
        if (description == null) {
            throw new NullPointerException("description");
        } else {
            this.description = description;
        }
    }
    public static <T> ConstructorExample<T> of(@NonNull T description) {
        return new ConstructorExample(description);
    }
}

@AllArgsConstructor

想要初始化所有字段。

@AllArgsConstructor(access = AccessLevel.PROTECTED)
public class ConstructorExample<T> {
    private int x, y;
    @NonNull
    private T description;
}

最终生成代码如下：

public class ConstructorExample<T> {
    private int x;
    private int y;
    @NonNull
    private T description;
    protected ConstructorExample(int x, int y, @NonNull T description) {
        if (description == null) {
            throw new NullPointerException("description");
        } else {
            this.x = x;
            this.y = y;
            this.description = description;
        }
    }
}

必用项@Data

@Data是一个集合体。包含Getter,Setter,RequiredArgsConstructor,ToString,EqualsAndHashCode

不可变对象valueobject @Value

这个看起来很美好，就是可以帮忙生成一个不可变对象。对于所有的字段都将生成final的。但我感觉有点失控。注解的优势应该是所见即所得，可以通过字面量来传递消息。而@Value字段给字段加final会让人困惑，因为这更改了我们的定义。当我想声明一个Immutable对象的时候，我会显示的给字段加一个限定final。

同@Data， @Value是一个集合体。包含Getter,AllArgsConstructor,ToString,EqualsAndHashCode。

/**
 * Created by Ryan Miao on 1/18/18.
 */
@Value
public class Room {
    @NonNull
    private String id;
    private String name;
    private boolean active;
    private Date createTime;

}

编译后

public final class Room {
    @NonNull
    private final String id;
    private final String name;
    private final boolean active;
    private final Date createTime;

    public Room(@NonNull String id, String name, boolean active, Date createTime) {
        if (id == null) {
            throw new NullPointerException("id");
        } else {
            this.id = id;
            this.name = name;
            this.active = active;
            this.createTime = createTime;
        }
    }

    @NonNull
    public String getId() {
        return this.id;
    }

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

    public boolean isActive() {
        return this.active;
    }

    public Date getCreateTime() {
        return this.createTime;
    }

    public boolean equals(Object o) {
        if (o == this) {
            return true;
        } else if (!(o instanceof Room)) {
            return false;
        } else {
            Room other = (Room)o;
            Object this$id = this.getId();
            Object other$id = other.getId();
            if (this$id == null) {
                if (other$id != null) {
                    return false;
                }
            } else if (!this$id.equals(other$id)) {
                return false;
            }

            label41: {
                Object this$name = this.getName();
                Object other$name = other.getName();
                if (this$name == null) {
                    if (other$name == null) {
                        break label41;
                    }
                } else if (this$name.equals(other$name)) {
                    break label41;
                }

                return false;
            }

            if (this.isActive() != other.isActive()) {
                return false;
            } else {
                Object this$createTime = this.getCreateTime();
                Object other$createTime = other.getCreateTime();
                if (this$createTime == null) {
                    if (other$createTime != null) {
                        return false;
                    }
                } else if (!this$createTime.equals(other$createTime)) {
                    return false;
                }

                return true;
            }
        }
    }

    public int hashCode() {
        int PRIME = true;
        int result = 1;
        Object $id = this.getId();
        int result = result * 59 + ($id == null ? 43 : $id.hashCode());
        Object $name = this.getName();
        result = result * 59 + ($name == null ? 43 : $name.hashCode());
        result = result * 59 + (this.isActive() ? 79 : 97);
        Object $createTime = this.getCreateTime();
        result = result * 59 + ($createTime == null ? 43 : $createTime.hashCode());
        return result;
    }

    public String toString() {
        return "Room(id=" + this.getId() + ", name=" + this.getName() + ", active=" + this.isActive() + ", createTime=" + this.getCreateTime() + ")";
    }
}

 

最喜欢的项 @Builder

对于喜欢builder模式的人来说，声明式简化对象创建流程让一切看得美好。但是，手动复制字段，手动创建方法很让人不喜。@Builder解决了刚需。

/**
 * Created by Ryan Miao on 1/18/18.
 */
@Data
@Builder(toBuilder = true)
public class Room {
    @NonNull
    private String id;
    private String name;
    private boolean active;
    private Date createTime;
    @Singular
    private Set<String> occupations;

    public static void main(String[] args) {
        Room room = Room.builder().active(true)
                .name("name")
                .id("id")
                .createTime(new Date())
                .occupation("1")
                .occupation("2")
                .build();

        Assert.assertEquals(2, room.getOccupations().size());

    }
}

这才是我们想要的建造者。对应生成的代码为：

//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//

package com.test.lombok;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.LinkedHashSet;
import java.util.Set;
import lombok.NonNull;
import org.junit.Assert;

public class Room {
    @NonNull
    private String id;
    private String name;
    private boolean active;
    private Date createTime;
    private Set<String> occupations;

    public static void main(String[] args) {
        Room room = builder().active(true).name("name").id("id").createTime(new Date()).occupation("1").occupation("2").build();
        Assert.assertEquals(2L, (long)room.getOccupations().size());
    }

    Room(@NonNull String id, String name, boolean active, Date createTime, Set<String> occupations) {
        if (id == null) {
            throw new NullPointerException("id");
        } else {
            this.id = id;
            this.name = name;
            this.active = active;
            this.createTime = createTime;
            this.occupations = occupations;
        }
    }

    public static Room.RoomBuilder builder() {
        return new Room.RoomBuilder();
    }

    public Room.RoomBuilder toBuilder() {
        return (new Room.RoomBuilder()).id(this.id).name(this.name).active(this.active).createTime(this.createTime).occupations(this.occupations);
    }

    @NonNull
    public String getId() {
        return this.id;
    }

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

    public boolean isActive() {
        return this.active;
    }

    public Date getCreateTime() {
        return this.createTime;
    }

    public Set<String> getOccupations() {
        return this.occupations;
    }

    public void setId(@NonNull String id) {
        if (id == null) {
            throw new NullPointerException("id");
        } else {
            this.id = id;
        }
    }

    public void setName(String name) {
        this.name = name;
    }

    public void setActive(boolean active) {
        this.active = active;
    }

    public void setCreateTime(Date createTime) {
        this.createTime = createTime;
    }

    public void setOccupations(Set<String> occupations) {
        this.occupations = occupations;
    }

    public boolean equals(Object o) {
        if (o == this) {
            return true;
        } else if (!(o instanceof Room)) {
            return false;
        } else {
            Room other = (Room)o;
            if (!other.canEqual(this)) {
                return false;
            } else {
                label63: {
                    Object this$id = this.getId();
                    Object other$id = other.getId();
                    if (this$id == null) {
                        if (other$id == null) {
                            break label63;
                        }
                    } else if (this$id.equals(other$id)) {
                        break label63;
                    }

                    return false;
                }

                Object this$name = this.getName();
                Object other$name = other.getName();
                if (this$name == null) {
                    if (other$name != null) {
                        return false;
                    }
                } else if (!this$name.equals(other$name)) {
                    return false;
                }

                if (this.isActive() != other.isActive()) {
                    return false;
                } else {
                    Object this$createTime = this.getCreateTime();
                    Object other$createTime = other.getCreateTime();
                    if (this$createTime == null) {
                        if (other$createTime != null) {
                            return false;
                        }
                    } else if (!this$createTime.equals(other$createTime)) {
                        return false;
                    }

                    Object this$occupations = this.getOccupations();
                    Object other$occupations = other.getOccupations();
                    if (this$occupations == null) {
                        if (other$occupations != null) {
                            return false;
                        }
                    } else if (!this$occupations.equals(other$occupations)) {
                        return false;
                    }

                    return true;
                }
            }
        }
    }

    protectedbooleancanEqual(Object other) {
        return other instanceof Room;
    }

    publicinthashCode() {
        int PRIME = true;
        int result = 1;
        Object $id = this.getId();
        int result = result * 59 + ($id == null ? 43 : $id.hashCode());
        Object $name = this.getName();
        result = result * 59 + ($name == null ? 43 : $name.hashCode());
        result = result * 59 + (this.isActive() ? 79 : 97);
        Object $createTime = this.getCreateTime();
        result = result * 59 + ($createTime == null ? 43 : $createTime.hashCode());
        Object $occupations = this.getOccupations();
        result = result * 59 + ($occupations == null ? 43 : $occupations.hashCode());
        return result;
    }

    public String toString() {
        return "Room(id=" + this.getId() + ", name=" + this.getName() + ", active=" + this.isActive() + ", createTime=" + this.getCreateTime() + ", occupations=" + this.getOccupations() + ")";
    }

    public static classRoomBuilder {
        private String id;
        private String name;
        private boolean active;
        private Date createTime;
        private ArrayList<String> occupations;

        RoomBuilder() {
        }

        public Room.RoomBuilderid(String id) {
            this.id = id;
            return this;
        }

        public Room.RoomBuildername(String name) {
            this.name = name;
            return this;
        }

        public Room.RoomBuilderactive(boolean active) {
            this.active = active;
            return this;
        }

        public Room.RoomBuildercreateTime(Date createTime) {
            this.createTime = createTime;
            return this;
        }

        public Room.RoomBuilderoccupation(String occupation) {
            if (this.occupations == null) {
                this.occupations = new ArrayList();
            }

            this.occupations.add(occupation);
            return this;
        }

        public Room.RoomBuilderoccupations(Collection<? extends String> occupations) {
            if (this.occupations == null) {
                this.occupations = new ArrayList();
            }

            this.occupations.addAll(occupations);
            return this;
        }

        public Room.RoomBuilderclearOccupations() {
            if (this.occupations != null) {
                this.occupations.clear();
            }

            return this;
        }

        public Room build() {
            Set occupations;
            switch(this.occupations == null ? 0 : this.occupations.size()) {
            case 0:
                occupations = Collections.emptySet();
                break;
            case 1:
                occupations = Collections.singleton(this.occupations.get(0));
                break;
            default:
                Set<String> occupations = new LinkedHashSet(this.occupations.size() < 1073741824 ? 1 + this.occupations.size() + (this.occupations.size() - 3) / 3 : 2147483647);
                occupations.addAll(this.occupations);
                occupations = Collections.unmodifiableSet(occupations);
            }

            return new Room(this.id, this.name, this.active, this.createTime, occupations);
        }

        public String toString() {
            return "Room.RoomBuilder(id=" + this.id + ", name=" + this.name + ", active=" + this.active + ", createTime=" + this.createTime + ", occupations=" + this.occupations + ")";
        }
    }
}

 

总结

lombok还提供了其他几个注解，以及还有好多内置的参数没有讲解。但是，根据2-8原理，我们根本不需要。上面这几个足够了。更多的注解只会增加理解阅读难度。

 

参考

https://projectlombok.org/features/all

http://kriszhang.com/lombok/