⭐表示重要。

第一章：Lombok 是什么？

官网。
官网介绍：
- 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.
翻译：
- Project Lombok 是一个 java 库，可以自动插入编辑器和构建工具，从而增强 java 的功能。
- 永远不要再写额外的 getter 或 equals 方法，用一个注解注释你的类让其有一个功能齐全的构建者模式，自动化你的日志记录变量，等等。
白话：Lombok 是一个 Java 实用工具，可以用来帮助开发人员消除 Java 中的冗长代码，尤其是对于简单的 Java 对象（POJO），它通过 注解 实现这一目的。
对比：
- 没有使用 Lombok ： ```java package com.github.fairy.era.bean;

import java.util.Objects;

/**

@author 许大仙
@version 1.0

@since 2021-11-21 08:16 */ public class UserOld {

private Integer id;

private String userName;

private String password;

private String phone;

private String email;

public UserOld() { }

public Integer getId() {

 return id;

}

public void setId(Integer id) {

 this.id = id;

}

public String getUserName() {

 return userName;

}

public void setUserName(String userName) {

 this.userName = userName;

}

public String getPassword() {

 return password;

}

public void setPassword(String password) {

 this.password = password;

}

public String getPhone() {

 return phone;

}

public void setPhone(String phone) {

 this.phone = phone;

}

public String getEmail() {

 return email;

}

public void setEmail(String email) {

 this.email = email;

}

@Override public boolean equals(Object o) {

 if (this == o) {
     return true;
 }
 if (o == null || getClass() != o.getClass()) {
     return false;
 }
 UserOld userOld = (UserOld) o;
 return Objects.equals(id, userOld.id) && Objects.equals(userName, userOld.userName) && Objects.equals(password, userOld.password) && Objects.equals(phone, userOld.phone) && Objects.equals(email, userOld.email);

}

@Override public int hashCode() {

 return Objects.hash(id, userName, password, phone, email);

}

@Override public String toString() {

 return "UserOld{" +
         "id=" + id +
         ", userName='" + userName + '\'' +
         ", password='" + password + '\'' +
         ", phone='" + phone + '\'' +
         ", email='" + email + '\'' +
         '}';

} } ```

使用了 Lombok ： ```java package com.github.fairy.era.bean;

import lombok.Data;

/**

@author 许大仙
@version 1.0
@since 2021-11-21 08:19 */ @Data public class User { private Integer id;

private String userName;

private String password;

private String phone;

private String email; } ```

第二章：Lombok 的原理

JSR 269：插件化注解处理 API（Pluggable Annotation Processing API）。
在 JSR 269 之前可以使用注解，但必须借助反射机制，而反射的方法局限性较大，由于必须定义 @Retention 为 RetentionPolicy.RUNTIME ，只能在 运行期 通过反射来获取注解值，使得运行时代码效率降低。
其次，如果想在编译阶段利用注解来进行一些检查，对用户的某些不合理代码给出错误报告，反射的使用方法就无能为力了。
而 JSR 269 之后我们可以在 javac 的 编译期 利用注解做这些事情。

Lombok的原理.png

第三章：Lombok的安装

IDEA 2021+ 中已经集成了 Lombok 插件了，无需安装。
Maven 的 pom.xml

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.18.22</version>
</dependency>

第四章：Lombok的特性（⭐）

4.1 @Getter 和 @Setter

@Getter 或 @Setter 标注成员变量，以使 Lombok 自动生成默认的 getter 和 setter。
@Getter 和 @Setter 可以作用于类或属性。
示例：
User.java

package com.github.fairy.era.bean;

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

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
public class User {
    @Getter
    @Setter
    private Integer id;

    @Getter(AccessLevel.PRIVATE)
    @Setter(AccessLevel.PACKAGE)
    private String userName;

    private String password;

    private String phone;

    private String email;
}

生成的代码：

package com.github.fairy.era.bean;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

    public Integer getId() {
        return this.id;
    }

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

    private String getUserName() {
        return this.userName;
    }

    void setUserName(String userName) {
        this.userName = userName;
    }
}

示例：
User.java

package com.github.fairy.era.bean;

import lombok.Getter;
import lombok.Setter;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@Setter
@Getter
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;
}

生成的代码：

package com.github.fairy.era.bean;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

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

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    public Integer getId() {
        return this.id;
    }

    public String getUserName() {
        return this.userName;
    }

    public String getPassword() {
        return this.password;
    }

    public String getPhone() {
        return this.phone;
    }

    public String getEmail() {
        return this.email;
    }
}

4.2 @ToString

@ToString 生成 toString() 方法。
@ToString 作用于类上。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.ToString;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@ToString
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;
}

生成的代码：

package com.github.fairy.era.bean;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

    public String toString() {
        return "User(id=" + this.id + ", userName=" + this.userName + ", password=" + this.password + ", phone=" + this.phone + ", email=" + this.email + ")";
    }
}

4.3 @EqualsAndHashCode

@EqualsAndHashCode 生成 equals() 和 hashCode() 方法。
@EqualsAndHashCode 作用于类上。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.EqualsAndHashCode;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@EqualsAndHashCode(exclude = {"phone", "email", "password"})
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;
}

生成的代码：

package com.github.fairy.era.bean;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

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

                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());
        return result;
    }
}

4.4 @NoArgsConstructor

@NoArgsConstructor 自动生成无参构造方法。
@NoArgsConstructor 作用于类上。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.NoArgsConstructor;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@NoArgsConstructor
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;

}

生成的代码：

package com.github.fairy.era.bean;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }
}

4.5 @RequiredArgsConstructor

@RequiredArgsConstructor 生成一个包含常量（final）和标识了 @NotNull 变量的构造方法。
@RequiredArgsConstructor 作用于类上。
应用场景：Spring 推荐使用构造器注入，那么只需要将需要注入的属性设置为 private final 的，然后在 handler 、serivce 等上面使用此注解即可完成自动装配。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.NonNull;
import lombok.RequiredArgsConstructor;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@RequiredArgsConstructor
public class User {

    private Integer id;

    @NonNull
    private String userName;

    private final String password;

    private String phone;

    private String email;

}

生成的代码：

package com.github.fairy.era.bean;

import lombok.NonNull;

public class User {
    private Integer id;
    @NonNull
    private String userName;
    private final String password;
    private String phone;
    private String email;

    public User(@NonNull String userName, String password) {
        if (userName == null) {
            throw new NullPointerException("userName is marked non-null but is null");
        } else {
            this.userName = userName;
            this.password = password;
        }
    }
}

4.6 @AllArgsConstructor

@AllArgsConstructor 自动生成全参数的构造函数。
@AllArgsConstructor 作用于类上。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.AllArgsConstructor;
import lombok.NonNull;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@AllArgsConstructor
public class User {

    private Integer id;

    @NonNull
    private String userName;

    private final String password;

    private String phone;

    private String email;

}

生成的代码：

package com.github.fairy.era.bean;

import lombok.NonNull;

public class User {
    private Integer id;
    @NonNull
    private String userName;
    private final String password;
    private String phone;
    private String email;

    public User(Integer id, @NonNull String userName, String password, String phone, String email) {
        if (userName == null) {
            throw new NullPointerException("userName is marked non-null but is null");
        } else {
            this.id = id;
            this.userName = userName;
            this.password = password;
            this.phone = phone;
            this.email = email;
        }
    }
}

4.7 @NonNull

@NonNull 会判断是否为 null ，如果为 null ，则会抛出 java.lang.NullPointerException。
@NonNull 作用于属性、方法、参数、局部变量、任意语句中。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.NonNull;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;

    public void test(@NonNull String s){
        System.out.println(s);
    }

}

生成的代码：

package com.github.fairy.era.bean;

import lombok.NonNull;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

    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);
        }
    }
}

4.8 @Data

@Data = @Setter + @Getter+@RequiredArgsConstructor + @ToString + @EqualsAndHashCode 。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.Data;
import lombok.NonNull;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@Data
public class User {

    private Integer id;

    @NonNull
    private String userName;

    private final String password;

    private String phone;

    private String email;

}

生成的代码：

package com.github.fairy.era.bean;

import lombok.NonNull;

public class User {
    private Integer id;
    @NonNull
    private String userName;
    private final String password;
    private String phone;
    private String email;

    public User(@NonNull String userName, String password) {
        if (userName == null) {
            throw new NullPointerException("userName is marked non-null but is null");
        } else {
            this.userName = userName;
            this.password = password;
        }
    }

    public Integer getId() {
        return this.id;
    }

    @NonNull
    public String getUserName() {
        return this.userName;
    }

    public String getPassword() {
        return this.password;
    }

    public String getPhone() {
        return this.phone;
    }

    public String getEmail() {
        return this.email;
    }

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

    public void setUserName(@NonNull String userName) {
        if (userName == null) {
            throw new NullPointerException("userName is marked non-null but is null");
        } else {
            this.userName = userName;
        }
    }

    public void setPhone(String phone) {
        this.phone = phone;
    }

    public void setEmail(String email) {
        this.email = email;
    }

    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 {
                label71: {
                    Object this$id = this.getId();
                    Object other$id = other.getId();
                    if (this$id == null) {
                        if (other$id == null) {
                            break label71;
                        }
                    } else if (this$id.equals(other$id)) {
                        break label71;
                    }

                    return false;
                }

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

                label57: {
                    Object this$password = this.getPassword();
                    Object other$password = other.getPassword();
                    if (this$password == null) {
                        if (other$password == null) {
                            break label57;
                        }
                    } else if (this$password.equals(other$password)) {
                        break label57;
                    }

                    return false;
                }

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

                Object this$email = this.getEmail();
                Object other$email = other.getEmail();
                if (this$email == null) {
                    if (other$email == null) {
                        return true;
                    }
                } else if (this$email.equals(other$email)) {
                    return true;
                }

                return false;
            }
        }
    }

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

    public int hashCode() {
        int PRIME = true;
        int result = 1;
        Object $id = this.getId();
        int result = result * 59 + ($id == null ? 43 : $id.hashCode());
        Object $userName = this.getUserName();
        result = result * 59 + ($userName == null ? 43 : $userName.hashCode());
        Object $password = this.getPassword();
        result = result * 59 + ($password == null ? 43 : $password.hashCode());
        Object $phone = this.getPhone();
        result = result * 59 + ($phone == null ? 43 : $phone.hashCode());
        Object $email = this.getEmail();
        result = result * 59 + ($email == null ? 43 : $email.hashCode());
        return result;
    }

    public String toString() {
        Integer var10000 = this.getId();
        return "User(id=" + var10000 + ", userName=" + this.getUserName() + ", password=" + this.getPassword() + ", phone=" + this.getPhone() + ", email=" + this.getEmail() + ")";
    }
}

4.9 @Builder

@Builder 使用构造者模式生成对象。
@Builder 作用于类、方法和构造器上。

示例：
User.java

package com.github.fairy.era.bean;

import lombok.Builder;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@Builder
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;

}

生成的代码：

package com.github.fairy.era.bean;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    User(Integer id, String userName, String password, String phone, String email) {
        this.id = id;
        this.userName = userName;
        this.password = password;
        this.phone = phone;
        this.email = email;
    }

    public static User.UserBuilder builder() {
        return new User.UserBuilder();
    }

    public static class UserBuilder {
        private Integer id;
        private String userName;
        private String password;
        private String phone;
        private String email;

        UserBuilder() {
        }

        public User.UserBuilder id(Integer id) {
            this.id = id;
            return this;
        }

        public User.UserBuilder userName(String userName) {
            this.userName = userName;
            return this;
        }

        public User.UserBuilder password(String password) {
            this.password = password;
            return this;
        }

        public User.UserBuilder phone(String phone) {
            this.phone = phone;
            return this;
        }

        public User.UserBuilder email(String email) {
            this.email = email;
            return this;
        }

        public User build() {
            return new User(this.id, this.userName, this.password, this.phone, this.email);
        }

        public String toString() {
            return "User.UserBuilder(id=" + this.id + ", userName=" + this.userName + ", password=" + this.password + ", phone=" + this.phone + ", email=" + this.email + ")";
        }
    }
}

4.10 @Value

@Value 类似于 @Data ，但是生成的属性是 final 类型的。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.Value;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@Value
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;

}

生成的代码：

package com.github.fairy.era.bean;

public final class User {
    private final Integer id;
    private final String userName;
    private final String password;
    private final String phone;
    private final String email;

    public User(Integer id, String userName, String password, String phone, String email) {
        this.id = id;
        this.userName = userName;
        this.password = password;
        this.phone = phone;
        this.email = email;
    }

    public Integer getId() {
        return this.id;
    }

    public String getUserName() {
        return this.userName;
    }

    public String getPassword() {
        return this.password;
    }

    public String getPhone() {
        return this.phone;
    }

    public String getEmail() {
        return this.email;
    }

    public boolean equals(Object o) {
        if (o == this) {
            return true;
        } else if (!(o instanceof User)) {
            return false;
        } else {
            User other = (User)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;
            }

            label61: {
                Object this$userName = this.getUserName();
                Object other$userName = other.getUserName();
                if (this$userName == null) {
                    if (other$userName == null) {
                        break label61;
                    }
                } else if (this$userName.equals(other$userName)) {
                    break label61;
                }

                return false;
            }

            label54: {
                Object this$password = this.getPassword();
                Object other$password = other.getPassword();
                if (this$password == null) {
                    if (other$password == null) {
                        break label54;
                    }
                } else if (this$password.equals(other$password)) {
                    break label54;
                }

                return false;
            }

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

            Object this$email = this.getEmail();
            Object other$email = other.getEmail();
            if (this$email == null) {
                if (other$email != null) {
                    return false;
                }
            } else if (!this$email.equals(other$email)) {
                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 $userName = this.getUserName();
        result = result * 59 + ($userName == null ? 43 : $userName.hashCode());
        Object $password = this.getPassword();
        result = result * 59 + ($password == null ? 43 : $password.hashCode());
        Object $phone = this.getPhone();
        result = result * 59 + ($phone == null ? 43 : $phone.hashCode());
        Object $email = this.getEmail();
        result = result * 59 + ($email == null ? 43 : $email.hashCode());
        return result;
    }

    public String toString() {
        Integer var10000 = this.getId();
        return "User(id=" + var10000 + ", userName=" + this.getUserName() + ", password=" + this.getPassword() + ", phone=" + this.getPhone() + ", email=" + this.getEmail() + ")";
    }
}

4.11 @Synchronized

@Synchronized 作用在方法上，自动添加到同步机制，生成的代码并不是直接锁方法而是锁代码块。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.Synchronized;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;

    @Synchronized
    public void sellTickets(){

    }

}

生成的代码：

package com.github.fairy.era.bean;

public class User {
    private final Object $lock = new Object[0];
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

    public void sellTickets() {
        synchronized(this.$lock) {
            ;
        }
    }
}

4.12 @Cleanup

@Cleanup 作用于局部变量，用于确保已分配的资源被释放，自动帮我们调用 close() 方法。比如 IO 的连接关闭。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.Cleanup;

import java.io.*;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;

    /** 复制文件
     * @param sources
     * @param aim
     * @throws IOException
     */
    public void copyFile(File sources, File aim) throws IOException {
        @Cleanup FileInputStream fis = new FileInputStream(sources);
        @Cleanup FileOutputStream fos = new FileOutputStream(aim);
        byte[] buf = new byte[1024];
        int len;
        while ((len = fis.read(buf)) != -1) {
            fos.write(buf, 0, len);
        }
    }

}

生成的代码：

package com.github.fairy.era.bean;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Collections;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

    public void copyFile(File sources, File aim) throws IOException {
        FileInputStream fis = new FileInputStream(sources);

        try {
            FileOutputStream fos = new FileOutputStream(aim);

            try {
                byte[] buf = new byte[1024];

                int len;
                while((len = fis.read(buf)) != -1) {
                    fos.write(buf, 0, len);
                }
            } finally {
                if (Collections.singletonList(fos).get(0) != null) {
                    fos.close();
                }

            }
        } finally {
            if (Collections.singletonList(fis).get(0) != null) {
                fis.close();
            }

        }

    }
}

4.13 @SneakyThrows

@SneakyThrows 作用于方法和构造器，用于抛出指定的异常，而不需要手动捕获异常，然后抛出。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.Cleanup;
import lombok.SneakyThrows;

import java.io.*;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;

    /** 复制文件
     * @param sources
     * @param aim
     */
    @SneakyThrows
    public void copyFile(File sources, File aim)  {
        @Cleanup FileInputStream fis = new FileInputStream(sources);
        @Cleanup FileOutputStream fos = new FileOutputStream(aim);
        byte[] buf = new byte[1024];
        int len;
        while ((len = fis.read(buf)) != -1) {
            fos.write(buf, 0, len);
        }
    }

}

生成的代码：

package com.github.fairy.era.bean;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.Collections;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

    public void copyFile(File sources, File aim) {
        try {
            FileInputStream fis = new FileInputStream(sources);

            try {
                FileOutputStream fos = new FileOutputStream(aim);

                try {
                    byte[] buf = new byte[1024];

                    int len;
                    while((len = fis.read(buf)) != -1) {
                        fos.write(buf, 0, len);
                    }
                } finally {
                    if (Collections.singletonList(fos).get(0) != null) {
                        fos.close();
                    }

                }
            } finally {
                if (Collections.singletonList(fis).get(0) != null) {
                    fis.close();
                }

            }

        } catch (Throwable var17) {
            throw var17;
        }
    }
}

4.14 @Log

@Log 、@Slf4j 、@Log4j 、@Log4j2 作用于类上，用于生成日志。
实际开发中，需要导入相关的依赖库。
示例：
User.java

package com.github.fairy.era.bean;

import lombok.Cleanup;
import lombok.SneakyThrows;
import lombok.extern.java.Log;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
@Log
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;

    /** 复制文件
     * @param sources
     * @param aim
     */
    @SneakyThrows
    public void copyFile(File sources, File aim)  {
        log.info("文件开始复制");
        @Cleanup FileInputStream fis = new FileInputStream(sources);
        @Cleanup FileOutputStream fos = new FileOutputStream(aim);
        byte[] buf = new byte[1024];
        int len;
        while ((len = fis.read(buf)) != -1) {
            fos.write(buf, 0, len);
        }
        log.info("文件结束复制");
    }

}

生成的代码：

package com.github.fairy.era.bean;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.util.Collections;
import java.util.logging.Logger;

public class User {
    private static final Logger log = Logger.getLogger(User.class.getName());
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

    public void copyFile(File sources, File aim) {
        try {
            log.info("文件开始复制");
            FileInputStream fis = new FileInputStream(sources);

            try {
                FileOutputStream fos = new FileOutputStream(aim);

                try {
                    byte[] buf = new byte[1024];

                    int len;
                    while((len = fis.read(buf)) != -1) {
                        fos.write(buf, 0, len);
                    }

                    log.info("文件结束复制");
                } finally {
                    if (Collections.singletonList(fos).get(0) != null) {
                        fos.close();
                    }

                }
            } finally {
                if (Collections.singletonList(fis).get(0) != null) {
                    fis.close();
                }

            }
        } catch (Throwable var17) {
            throw var17;
        }
    }
}

4.15 var

var 表示局部变量的类型推断，其实，在 JDK 9 中已经集成了该语法。
示例：
User.java

package com.github.fairy.era.bean;

import java.util.ArrayList;

/**
 * @author 许大仙
 * @version 1.0
 * @since 2021-11-21 08:19
 */
public class User {

    private Integer id;

    private String userName;

    private String password;

    private String phone;

    private String email;

    public void test() {
        var list = new ArrayList<String>();
        list.add("aa");
        list.add("bb");

        System.out.println("list = " + list);
    }

}

生成的代码：

package com.github.fairy.era.bean;

import java.util.ArrayList;

public class User {
    private Integer id;
    private String userName;
    private String password;
    private String phone;
    private String email;

    public User() {
    }

    public void test() {
        ArrayList<String> list = new ArrayList();
        list.add("aa");
        list.add("bb");
        System.out.println("list = " + list);
    }
}

Java学科

Lombok（v1.18.22）