1. Lombok簡介
官網地址：https://projectlombok.org/
Lombok項目是一個Java庫，它會自動插入您的編輯器和構建工具中，從而為你優化Java代碼。
所以可以不用再手寫一個getter、setter或equals方法。2. 變量使用介紹
2.1 val修飾變量
可以使用val作為局部變量聲明的類型，而不用實際編寫該類型。
當您執行此操作時，將從初始值設定項表達式中推斷出類型。
局部變量也將成為final類型的變量。
此功能僅適用於局部變量和foreach循環，不適用於字段。
val實際上是某種“類型”，在lombok包中作為真實類存在。 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: %s\n", entry.getKey(), entry.getValue());
}
}
}編譯成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: %s\n", entry.getKey(), entry.getValue());
}
}
}2.2 var修飾變量
var的工作原理與val完全相同，只是局部變量未標記為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: %s\n", entry.getKey(), entry.getValue());
}
}
}編譯成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: %s\n", new Object[] { entry.getKey(), entry.getValue() });
}
}
3. 註解使用介紹
3.1 @NonNull使用
可以在方法或構造器的參數上使用 @NonNull,lombok會為你生成一個空值檢查的聲明。
相當於=》
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;
}
}編譯成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來確保在代碼執行路徑退出當前作用域之前自動清除給定的資源。
其實就是關閉註解標註的當前資源。【簡單瞭解一下就行，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);
}
}
}編譯成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標註任何字段，lombok 可以幫助你自動生成默認的get、set方法。
默認的get、set方法是public的，除非你額外設置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);
}
}編譯成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
任何類的定義上都可以被@ToString標註，lombok可以生成一個toString()的實現方法。
默認打印類名以及每個字段並且用逗號分隔。 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;
}
}
}編譯成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
任何類的定義上都可以被@EqualsAndHashCode標註，lombok可以生成一個equals(Object other)和hashCode()的實現方法。
它將使用所有非靜態，非瞬態字段，但是您可以通過使用@ EqualsAndHashCode.Include或@EqualsAndHashCode標記類型成員來修改使用的字段。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;
}
}
}編譯成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
這組3個註釋會生成一個構造函數，該構造函數將為某些字段接受1個參數，並將該參數簡單地分配給該字段。
@NoArgsConstructor 將生成沒有參數的構造器；
@RequiredArgsConstructor 為需要特殊處理的每個字段生成一個帶有1個參數的構造函數；
@AllArgsConstructor 為類中的每個字段生成一個帶有1個參數的構造函數。 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;
}
}編譯成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是一個方便的快捷方式註釋，它將@ ToString，@ EqualsAndHashCode，@ Getter / @Setter和@RequiredArgsConstructor的功能捆綁在一起.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;
}
}編譯成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的不可變形式； 默認情況下，所有字段都設為私有和final的字段，並且不會生成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;
}
}編譯成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註釋會為您的類生成複雜的構建器API。
@Builder可自動生成使你的類可被實例化的代碼。 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;
}編譯成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可用於偷偷地拋出已檢查的異常，而無需在方法的throws子句中實際聲明。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();
}
}編譯成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是同步方法修飾符的更安全的變體。
與同步一樣，註釋只能在靜態和實例方法上使用。 它的操作類似於synchronized關鍵字，但是它鎖定在不同的對象上 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");
}
}編譯成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.
說實話沒看明白這段話是什麼意思，個人理解為：在類的字段上標註 @With 註解之後，將會自動生成一個 withFieldName(newValue) 的方法，該方法會基於 newValue 調用相應構造函數，創建一個當前類對應的實例。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;
}
}編譯成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 註解支持一個 lazy 屬性，該屬性默認為 false。當設置為 true 時，會啟用延遲初始化，即當首次調用 getter 方法時才進行初始化。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;
}
}編譯成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註釋用於配置lombok如何生成和查找getter和setter。
默認情況下，lombok遵循針對getter和setter的bean規範：例如，名為Pepper的字段的getter是getPepper。 但是，有些人可能希望打破bean規範，以得到更好看的API。 @Accessors提供3種方式:
fluent--》 一個布爾值。如果為真，pepper的getter就是 pepper()，setter方法就是pepper(T newValue)。並且，除非特別說明，chain默認為真。
chain--》 一個布爾值。如果為真，產生的setter返回的this而不是void。默認是假。如果fluent=true，那麼chain默認為真。
prefix--》 一系列string類型。如果顯示，屬性必須加上某些定義的前綴。 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!";
}編譯成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;
}
}