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Lombok项目是一个Java库，它会自动插入您的编辑器和构建工具中，从而为你优化Java代码。 所以可以不用再手写一个getter、setter或equals方法。2. 变量使用介绍2.1 val修饰变量可以使用val作为局部变量声明的类型，而不用实际编写该类型。 当您执行此操作时，将从初始值设定项表达式中推断出类型。 局部变量也将成为final类型的变量。 此功能仅适用于局部变量和foreach循环，不适用于字段。 val实际上是某种“类型”，在lombok包中作为真实类存在。使用lombok方式：
import java.util.ArrayList; import java.util.HashMap; import lombok.val; public class ValExample { public String example() { val example = new ArrayList<String>(); example.add("Hello, World!"); val foo = example.get(0); return foo.toLowerCase(); } public void example2() { val map = new HashMap<Integer, String>(); map.put(0, "zero"); map.put(5, "five"); for (val entry : map.entrySet()) { System.out.printf("%d: %sn", entry.getKey(), entry.getValue()); } } }编译成Java方式：
import java.util.ArrayList; import java.util.HashMap; import java.util.Map; public class ValExample { public String example() { final ArrayList<String> example = new ArrayList<String>(); example.add("Hello, World!"); final String foo = example.get(0); return foo.toLowerCase(); } public void example2() { final HashMap<Integer, String> map = new HashMap<Integer, String>(); map.put(0, "zero"); map.put(5, "five"); for (final Map.Entry<Integer, String> entry : map.entrySet()) { System.out.printf("%d: %sn", entry.getKey(), entry.getValue()); } } }2.2 var修饰变量var的工作原理与val完全相同，只是局部变量未标记为final。使用lombok方式：
import java.util.ArrayList; import java.util.HashMap; import lombok.var; public class VarExample { public String example() { var example = new ArrayList<String>(); example.add("Hello, World!"); var foo = example.get(0); return foo.toLowerCase(); } public void example2() { var map = new HashMap<Integer, String>(); map.put(0, "zero"); map.put(5, "five"); for (var entry : map.entrySet()) { System.out.printf("%d: %sn", entry.getKey(), entry.getValue()); } } }编译成Java方式：
import java.util.ArrayList; import java.util.HashMap; import java.util.Map; public class VarExample { public String example() { ArrayList<String> example = new ArrayList<String>(); example.add("Hello, World!"); String foo = (String)example.get(0); return foo.toLowerCase(); } public void example2() { HashMap<Integer, String> map = new HashMap<Integer, String>(); map.put(Integer.valueOf(0), "zero"); map.put(Integer.valueOf(5), "five"); for (Map.Entry<Integer, String> entry : map.entrySet()) { System.out.printf("%d: %sn", new Object[] { entry.getKey(), entry.getValue() }); } }3. 注解使用介绍3.1 @NonNull使用可以在方法或构造器的参数上使用 @NonNull,lombok会为你生成一个空值检查的声明。 相当于=》 if (param == null) { throw new NullPointerException("param is marked @NonNull but is null"); }使用lombok方式：
import lombok.NonNull; public class NonNullExample { private String name; public NonNullExample(@NonNull String person) { this.name = person; } }编译成Java方式：
import lombok.NonNull; public class NonNullExample { public NonNullExample(@NonNull String person) { if (person == null) throw new NullPointerException("person is marked non-null but is null"); this.name = person; } private String name; }3.2 @Cleanup使用您可以使用@Cleanup来确保在代码执行路径退出当前作用域之前自动清除给定的资源。 其实就是关闭注解标注的当前资源。【简单了解一下就行，一般也用不上】使用lombok方式：
import lombok.Cleanup; import java.io.*; public class CleanupExample { public static void main(String[] args) throws IOException { @Cleanup InputStream in = new FileInputStream(args[0]); @Cleanup OutputStream out = new FileOutputStream(args[1]); byte[] b = new byte[10000]; while (true) { int r = in.read(b); if (r == -1) break; out.write(b, 0, r); } } }编译成Java方式：
import java.io.*; public class CleanupExample { public static void main(String[] args) throws IOException { InputStream in = new FileInputStream(args[0]); try { OutputStream out = new FileOutputStream(args[1]); try { byte[] b = new byte[10000]; while (true) { int r = in.read(b); if (r == -1) break; out.write(b, 0, r); } } finally { if (out != null) { out.close(); } } } finally { if (in != null) { in.close(); } } } }3.3 @Getter and @Setter可以使用@Getter 或 @Setter标注任何字段，lombok 可以帮助你自动生成默认的get、set方法。 默认的get、set方法是public的，除非你额外设置AccessLevel使用lombok方式：
import lombok.AccessLevel; import lombok.Getter; import lombok.Setter; 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; /** * 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); } }编译成Java方式：
public class GetterSetterExample { /** * Age of the person. Water is wet. */ private int age = 10; /** * Name of the person. */ private String name; @Override public String toString() { return String.format("%s (age: %d)", name, age); } /** * Age of the person. Water is wet. * * @return The current value of this person's age. Circles are round. */ public int getAge() { return age; } /** * Age of the person. Water is wet. * * @param age New value for this person's age. Sky is blue. */ public void setAge(int age) { this.age = age; } /** * Changes the name of this person. * * @param name The new value. */ protected void setName(String name) { this.name = name; } }3.4 @ToString使用任何类的定义上都可以被@ToString标注，lombok可以生成一个toString()的实现方法。 默认打印类名以及每个字段并且用逗号分隔。使用lombok方式：
import lombok.ToString; @ToString public class ToStringExample { private static final int STATIC_VAR = 10; private String name; private Shape shape = new Square(5, 10); private String[] tags; @ToString.Exclude private int id; public String getName() { return this.name; } @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; } } }编译成Java方式：
import java.util.Arrays; 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; public String getName() { return this.name; } 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 String toString() { return "Square(super=" + super.toString() + ", width=" + this.width + ", height=" + this.height + ")"; } } @Override public String toString() { return "ToStringExample(" + this.getName() + ", " + this.shape + ", " + Arrays.deepToString(this.tags) + ")"; } }3.5 @EqualsAndHashCode任何类的定义上都可以被@EqualsAndHashCode标注，lombok可以生成一个equals(Object other)和hashCode()的实现方法。 它将使用所有非静态，非瞬态字段，但是您可以通过使用@ EqualsAndHashCode.Include或@EqualsAndHashCode标记类型成员来修改使用的字段。使用lombok方式：
import lombok.EqualsAndHashCode; @EqualsAndHashCode public class EqualsAndHashCodeExample { private transient int transientVar = 10; private String name; private double score; @EqualsAndHashCode.Exclude private Shape shape = new Square(5, 10); private String[] tags; @EqualsAndHashCode.Exclude 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; } } }编译成Java方式：
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 ? 43 : 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; } } }3.6 @NoArgsConstructor、@RequiredArgsConstructor、 @AllArgsConstructor这组3个注释会生成一个构造函数，该构造函数将为某些字段接受1个参数，并将该参数简单地分配给该字段。 @NoArgsConstructor 将生成没有参数的构造器； @RequiredArgsConstructor 为需要特殊处理的每个字段生成一个带有1个参数的构造函数； @AllArgsConstructor 为类中的每个字段生成一个带有1个参数的构造函数。使用lombok方式：
import lombok.AccessLevel; import lombok.RequiredArgsConstructor; import lombok.AllArgsConstructor; import lombok.NonNull; @RequiredArgsConstructor(staticName = "of") @AllArgsConstructor(access = AccessLevel.PROTECTED) public class ConstructorExample<T> { private int x, y; @NonNull private T description; @NoArgsConstructor public static class NoArgsExample { @NonNull private String field; } }编译成Java方式：
public class ConstructorExample<T> { private int x, y; @NonNull private T description; private ConstructorExample(T description) { if (description == null) throw new NullPointerException("description"); this.description = description; } public static <T> ConstructorExample<T> of(T description) { return new ConstructorExample<T>(description); } @java.beans.ConstructorProperties({"x", "y", "description"}) protected ConstructorExample(int x, int y, T description) { if (description == null) throw new NullPointerException("description"); this.x = x; this.y = y; this.description = description; } public static class NoArgsExample { @NonNull private String field; public NoArgsExample() { } } }3.7 @Data使用@Data是一个方便的快捷方式注释，它将@ ToString，@ EqualsAndHashCode，@ Getter / @Setter和@RequiredArgsConstructor的功能捆绑在一起.使用lombok方式：
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; } }编译成Java方式：
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; } } }3.8 @Value使用@Value是@Data的不可变形式； 默认情况下，所有字段都设为私有和final的字段，并且不会生成setter。使用lombok方式：
import lombok.AccessLevel; import lombok.experimental.NonFinal; import lombok.experimental.Value; import lombok.experimental.Wither; import lombok.ToString; @Value public class ValueExample { String name; @Wither(AccessLevel.PACKAGE) @NonFinal int age; double score; protected String[] tags; @ToString(includeFieldNames=true) @Value(staticConstructor="of") public static class Exercise<T> { String name; T value; } }编译成Java方式：
import java.util.Arrays; public final class ValueExample { private final String name; private int age; private final double score; protected final String[] tags; @java.beans.ConstructorProperties({"name", "age", "score", "tags"}) public ValueExample(String name, int age, double score, String[] tags) { this.name = name; this.age = age; this.score = score; this.tags = tags; } public String getName() { return this.name; } public int getAge() { return this.age; } public double getScore() { return this.score; } public String[] getTags() { return this.tags; } @java.lang.Override public boolean equals(Object o) { if (o == this) return true; if (!(o instanceof ValueExample)) return false; final ValueExample other = (ValueExample)o; final Object this$name = this.getName(); final Object other$name = other.getName(); if (this$name == null ? other$name != null : !this$name.equals(other$name)) 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; } @java.lang.Override public int hashCode() { final int PRIME = 59; int result = 1; final Object $name = this.getName(); result = result * PRIME + ($name == null ? 43 : $name.hashCode()); result = result * PRIME + this.getAge(); final long $score = Double.doubleToLongBits(this.getScore()); result = result * PRIME + (int)($score >>> 32 ^ $score); result = result * PRIME + Arrays.deepHashCode(this.getTags()); return result; } @java.lang.Override public String toString() { return "ValueExample(name=" + getName() + ", age=" + getAge() + ", score=" + getScore() + ", tags=" + Arrays.deepToString(getTags()) + ")"; } ValueExample withAge(int age) { return this.age == age ? this : new ValueExample(name, age, score, tags); } public static final class Exercise<T> { private final String name; private final T value; private Exercise(String name, T value) { this.name = name; this.value = value; } public static <T> Exercise<T> of(String name, T value) { return new Exercise<T>(name, value); } public String getName() { return this.name; } public T getValue() { return this.value; } @java.lang.Override public boolean equals(Object o) { if (o == this) return true; if (!(o instanceof ValueExample.Exercise)) return false; final Exercise<?> other = (Exercise<?>)o; final Object this$name = this.getName(); final Object other$name = other.getName(); if (this$name == null ? other$name != null : !this$name.equals(other$name)) return false; final Object this$value = this.getValue(); final Object other$value = other.getValue(); if (this$value == null ? other$value != null : !this$value.equals(other$value)) return false; return true; } @java.lang.Override public int hashCode() { final int PRIME = 59; int result = 1; final Object $name = this.getName(); result = result * PRIME + ($name == null ? 43 : $name.hashCode()); final Object $value = this.getValue(); result = result * PRIME + ($value == null ? 43 : $value.hashCode()); return result; } @java.lang.Override public String toString() { return "ValueExample.Exercise(name=" + getName() + ", value=" + getValue() + ")"; } } }3.9 @Builder使用@Builder注释会为您的类生成复杂的构建器API。 @Builder可自动生成使你的类可被实例化的代码。使用lombok方式：
import lombok.Builder; import lombok.Singular; import java.util.Set; @Builder public class BuilderExample { @Builder.Default private long created = System.currentTimeMillis(); private String name; private int age; @Singular private Set<String> occupations; }编译成Java方式：
import java.util.Set; public class BuilderExample { private long created; private String name; private int age; private Set<String> occupations; BuilderExample(String name, int age, Set<String> occupations) { this.name = name; this.age = age; this.occupations = occupations; } private static long $default$created() { return System.currentTimeMillis(); } public static BuilderExampleBuilder builder() { return new BuilderExampleBuilder(); } public static class BuilderExampleBuilder { private long created; private boolean created$set; private String name; private int age; private java.util.ArrayList<String> occupations; BuilderExampleBuilder() { } public BuilderExampleBuilder created(long created) { this.created = created; this.created$set = true; return this; } public BuilderExampleBuilder name(String name) { this.name = name; return this; } public BuilderExampleBuilder age(int age) { this.age = age; return this; } public BuilderExampleBuilder occupation(String occupation) { if (this.occupations == null) { this.occupations = new java.util.ArrayList<String>(); } this.occupations.add(occupation); return this; } public BuilderExampleBuilder occupations(Collection<? extends String> occupations) { if (this.occupations == null) { this.occupations = new java.util.ArrayList<String>(); } this.occupations.addAll(occupations); return this; } public BuilderExampleBuilder clearOccupations() { if (this.occupations != null) { this.occupations.clear(); } return this; } public BuilderExample build() { // complicated switch statement to produce a compact properly sized immutable set omitted. Set<String> occupations = ...; return new BuilderExample(created$set ? created : BuilderExample.$default$created(), name, age, occupations); } @java.lang.Override public String toString() { return "BuilderExample.BuilderExampleBuilder(created = " + this.created + ", name = " + this.name + ", age = " + this.age + ", occupations = " + this.occupations + ")"; } } }3.10 @SneakyThrows@SneakyThrows可用于偷偷地抛出已检查的异常，而无需在方法的throws子句中实际声明。使用lombok方式：
import lombok.SneakyThrows; public class SneakyThrowsExample implements Runnable { @SneakyThrows(UnsupportedEncodingException.class) public String utf8ToString(byte[] bytes) { return new String(bytes, "UTF-8"); } @SneakyThrows public void run() { throw new Throwable(); } }编译成Java方式：
import lombok.Lombok; public class SneakyThrowsExample implements Runnable { public String utf8ToString(byte[] bytes) { try { return new String(bytes, "UTF-8"); } catch (UnsupportedEncodingException e) { throw Lombok.sneakyThrow(e); } } public void run() { try { throw new Throwable(); } catch (Throwable t) { throw Lombok.sneakyThrow(t); } } }3.11 @Synchronized使用@Synchronized是同步方法修饰符的更安全的变体。 与同步一样，注释只能在静态和实例方法上使用。 它的操作类似于synchronized关键字，但是它锁定在不同的对象上使用lombok方式：
import lombok.Synchronized; public class SynchronizedExample { private final Object readLock = new Object(); @Synchronized public static void hello() { System.out.println("world"); } @Synchronized public int answerToLife() { return 42; } @Synchronized("readLock") public void foo() { System.out.println("bar"); } }编译成Java方式：
public class SynchronizedExample { private static final Object $LOCK = new Object[0]; private final Object $lock = new Object[0]; private final Object readLock = new Object(); public static void hello() { synchronized($LOCK) { System.out.println("world"); } } public int answerToLife() { synchronized($lock) { return 42; } } public void foo() { synchronized(readLock) { System.out.println("bar"); } } }3.12 @With 使用The next best alternative to a setter for an immutable property is to construct a clone of the object, but with a new value for this one field. A method to generate this clone is precisely what @With generates: a withFieldName(newValue) method which produces a clone except for the new value for the associated field. 说实话没看明白这段话是什么意思，个人理解为：在类的字段上标注 @With 注解之后，将会自动生成一个 withFieldName(newValue) 的方法，该方法会基于 newValue 调用相应构造函数，创建一个当前类对应的实例。使用lombok方式：
import lombok.AccessLevel; import lombok.NonNull; import lombok.With; public class WithExample { @With(AccessLevel.PROTECTED) @NonNull private final String name; @With private final int age; public WithExample(String name, int age) { if (name == null) throw new NullPointerException(); this.name = name; this.age = age; } }编译成Java方式：
import lombok.NonNull; public class WithExample { private @NonNull final String name; private final int age; public WithExample(String name, int age) { if (name == null) throw new NullPointerException(); this.name = name; this.age = age; } protected WithExample withName(@NonNull String name) { if (name == null) throw new java.lang.NullPointerException("name"); return this.name == name ? this : new WithExample(name, age); } public WithExample withAge(int age) { return this.age == age ? this : new WithExample(name, age); } }3.13 @Getter(lazy=true)@Getter 注解支持一个 lazy 属性，该属性默认为 false。当设置为 true 时，会启用延迟初始化，即当首次调用 getter 方法时才进行初始化。使用lombok方式：
import lombok.Getter; public class GetterLazyExample { @Getter(lazy=true) private final double[] cached = expensive(); private double[] expensive() { double[] result = new double[1000000]; for (int i = 0; i < result.length; i++) { result[i] = Math.asin(i); } return result; } }编译成Java方式：
public class GetterLazyExample { private final java.util.concurrent.AtomicReference<java.lang.Object> cached = new java.util.concurrent.AtomicReference<java.lang.Object>(); public double[] getCached() { java.lang.Object value = this.cached.get(); if (value == null) { synchronized(this.cached) { value = this.cached.get(); if (value == null) { final double[] actualValue = expensive(); value = actualValue == null ? this.cached : actualValue; this.cached.set(value); } } } return (double[])(value == this.cached ? null : value); } private double[] expensive() { double[] result = new double[1000000]; for (int i = 0; i < result.length; i++) { result[i] = Math.asin(i); } return result; } }3.14 @Accessors使用@Accessors注释用于配置lombok如何生成和查找getter和setter。 默认情况下，lombok遵循针对getter和setter的bean规范：例如，名为Pepper的字段的getter是getPepper。 但是，有些人可能希望打破bean规范，以得到更好看的API。 @Accessors提供3种方式: fluent--》 一个布尔值。如果为真，pepper的getter就是 pepper()，setter方法就是pepper(T newValue)。并且，除非特别说明，chain默认为真。 chain--》 一个布尔值。如果为真，产生的setter返回的this而不是void。默认是假。如果fluent=true，那么chain默认为真。 prefix--》 一系列string类型。如果显示，属性必须加上某些定义的前缀。使用lombok方式：
import lombok.experimental.Accessors; import lombok.Getter; import lombok.Setter; @Accessors(fluent = true) public class AccessorsExample { @Getter @Setter private int age = 10; } class PrefixExample { @Accessors(prefix = "f") @Getter private String fName = "Hello, World!"; }编译成Java方式：
public class AccessorsExample { private int age = 10; public int age() { return this.age; } public AccessorsExample age(final int age) { this.age = age; return this; } } class PrefixExample { private String fName = "Hello, World!"; public String getName() { return this.fName; } } ---来自腾讯云社区的---践.行者
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