@Data
most commonly used annotation
@Data
public class Demo {
private Long id;
private String name;
}after compilation
public class Demo {
private Long id;
private String name;
public Demo() {
}
public Long getId() {
return this.id;
}
public String getName() {
return this.name;
}
public void setId(Long id) {
this.id = id;
}
public void setName(String name) {
this.name = name;
}
public boolean equals(Object o) {
if (o == this) {
return true;
} else if (!(o instanceof Demo)) {
return false;
} else {
Demo other = (Demo)o;
if (!other.canEqual(this)) {
return false;
} else {
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;
}
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;
}
return true;
}
}
}
protected boolean canEqual(Object other) {
return other instanceof Demo;
}
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());
return result;
}
public String toString() {
return "Demo(id=" + this.getId() + ", name=" + this.getName() + ")";
}
}@NonNull
public void setId(@NonNull Long id) {
this.id = id;
}after compilation
public void setId(@NonNull Long id) {
if (id == null) {
throw new NullPointerException("id");
} else {
this.id = id;
}
}
@RequiredArgsConstructor
@RequiredArgsConstructor
public class Demo {
@NonNull
private Long id;
private String name;
}after compilation
public class Demo {
@NonNull
private Long id;
private String name;
public Demo(@NonNull Long id) {
if (id == null) {
throw new NullPointerException("id");
} else {
this.id = id;
}
}
}@NoArgsConstructor @AllArgsConstructor
@NoArgsConstructor
@AllArgsConstructor
public class Demo {
@NonNull
private Long id;
private String name;
}after compilation
public class Demo {
@NonNull
private Long id;
private String name;
public Demo() {
}
public Demo(@NonNull Long id, String name) {
if (id == null) {
throw new NullPointerException("id");
} else {
this.id = id;
this.name = name;
}
}
}@Builder
When used alone, the constructor with full parameters is automatically generated. There is no default constructor. If you want to have a non-full parameter constructor, you must use it together with the @AllArgsConstructor annotation, and then add it manually or by annotation, otherwise it will not compile.
@Builder
public class Demo {
@NonNull
private Long id;
private String name;
}after compilation
public class Demo {
@NonNull
private Long id;
private String name;
Demo(@NonNull Long id, String name) {
if (id == null) {
throw new NullPointerException("id");
} else {
this.id = id;
this.name = name;
}
}
public static Demo.DemoBuilder builder() {
return new Demo.DemoBuilder();
}
public static class DemoBuilder {
private Long id;
private String name;
DemoBuilder() {
}
public Demo.DemoBuilder id(Long id) {
this.id = id;
return this;
}
public Demo.DemoBuilder name(String name) {
this.name = name;
return this;
}
public Demo build() {
return new Demo(this.id, this.name);
}
public String toString() {
return "Demo.DemoBuilder(id=" + this.id + ", name=" + this.name + ")";
}
}
}@Cleanup
automatically call close()
public static void main(String[] args) throws FileNotFoundException,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);
}
}after compilation
public static void main(String[] args) throws FileNotFoundException, IOException {
FileInputStream in = new FileInputStream(args[0]);
try {
FileOutputStream out = new FileOutputStream(args[1]);
try {
byte[] b = new byte[10000];
while(true) {
int r = in.read(b);
if (r == -1) {
return;
}
out.write(b, 0, r);
}
} finally {
if (Collections.singletonList(out).get(0) != null) {
out.close();
}
}
} finally {
if (Collections.singletonList(in).get(0) != null) {
in.close();
}
}
}@Synchronized
lock the method
public class Demo {
private final Object writeLock = new Object();
@Synchronized
public static void method1(){
System.out.println("method1");
}
@Synchronized
public void method2(){
System.out.println("method1");
}
@Synchronized("writeLock")
public void method3(){
System.out.println("method1");
}
}after compilation
public class Demo {
private static final Object $LOCK = new Object[0];
private final Object $lock = new Object[0];
private final Object writeLock = new Object();
public Demo() {
}
public static void method1() {
Object var0 = $LOCK;
synchronized($LOCK) {
System.out.println("method1");
}
}
public void method2() {
Object var1 = this.$lock;
synchronized(this.$lock) {
System.out.println("method1");
}
}
public void method3() {
Object var1 = this.writeLock;
synchronized(this.writeLock) {
System.out.println("method1");
}
}
}@Wither
To assign a final value, there must be a full-parameter constructor
@AllArgsConstructor
public class Demo {
@Wither
private final int number;
}after compilation
public class Demo {
private final int number;
public Demo(int number) {
this.number = number;
}
public Demo withNumber(int number) {
return this.number == number ? this : new Demo(number);
}
}@Log4j2@Log@Log4j@CommonsLog@Slf4j@XSLF4j
@Log4j2
public class Demo {
public static void main(String[] args) {
log.error("error");
}
}after compilation
public class Demo {
private static final Logger log = LogManager.getLogger(Demo.class);
public Demo() {
}
public static void main(String[] args) {
log.error("error");
}
}