十分钟搞懂Java效率工具Lombok使用与原理

<dependency>
    <groupId>org.projectlombok</groupId>
    <artifactId>lombok</artifactId>
    <version>1.16.8</version>
</dependency>

public static void main(String[] args) {
    val sets = new HashSet<String>();
    val lists = new ArrayList<String>();
    val maps = new HashMap<String, String>();
    //=>相当于如下
    final Set<String> sets2 = new HashSet<>();
    final List<String> lists2 = new ArrayList<>();
    final Map<String, String> maps2 = new HashMap<>();
}
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public void notNullExample(@NonNull String string) {
    string.length();
}
//=>相当于
public void notNullExample(String string) {
    if (string != null) {
        string.length();
    } else {
        throw new NullPointerException("null");
    }
}
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public static void main(String[] args) {
    try {
        @Cleanup InputStream inputStream = new FileInputStream(args[0]);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    }
    //=>相当于
    InputStream inputStream = null;
    try {
        inputStream = new FileInputStream(args[0]);
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } finally {
        if (inputStream != null) {
            try {
                inputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}
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@Setter(AccessLevel.PUBLIC)
@Getter(AccessLevel.PROTECTED)
private int id;
private String shap;
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@ToString(exclude = "id", callSuper = true, includeFieldNames = true)
public class LombokDemo {
    private int id;
    private String name;
    private int age;
    public static void main(String[] args) {
        //输出LombokDemo(super=LombokDemo@48524010, name=null, age=0)
        System.out.println(new LombokDemo());
    }
}
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@EqualsAndHashCode(exclude = {"id", "shape"}, callSuper = false)
public class LombokDemo {
    private int id;
    private String shap;
}
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@NoArgsConstructor
@RequiredArgsConstructor(staticName = "of")
@AllArgsConstructor
public class LombokDemo {
    @NonNull
    private int id;
    @NonNull
    private String shap;
    private int age;
    public static void main(String[] args) {
        new LombokDemo(1, "circle");
        //使用静态工厂方法
        LombokDemo.of(2, "circle");
        //无参构造
        new LombokDemo();
        //包含所有参数
        new LombokDemo(1, "circle", 2);
    }
}
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import lombok.Data;
@Data
public class Menu {
    private String shopId;
    private String skuMenuId;
    private String skuName;
    private String normalizeSkuName;
    private String dishMenuId;
    private String dishName;
    private String dishNum;
    //默认阈值
    private float thresHold = 0;
    //新阈值
    private float newThresHold = 0;
    //总得分
    private float totalScore = 0;
}
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@Value
public class LombokDemo {
    @NonNull
    private int id;
    @NonNull
    private String shap;
    private int age;
    //相当于
    private final int id;
    public int getId() {
        return this.id;
    }
    ...
}
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@Builder
public class BuilderExample {
    private String name;
    private int age;
    @Singular
    private Set<String> occupations;
    public static void main(String[] args) {
        BuilderExample test = BuilderExample.builder().age(11).name("test").build();
    }
}
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import lombok.SneakyThrows;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.io.UnsupportedEncodingException;
public class Test {
    @SneakyThrows()
    public void read() {
        InputStream inputStream = new FileInputStream("");
    }
    @SneakyThrows
    public void write() {
        throw new UnsupportedEncodingException();
    }
    //相当于
    public void read() throws FileNotFoundException {
        InputStream inputStream = new FileInputStream("");
    }
    public void write() throws UnsupportedEncodingException {
        throw new UnsupportedEncodingException();
    }
}
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public class SynchronizedDemo {
    @Synchronized
    public static void hello() {
        System.out.println("world");
    }
    //相当于
    private static final Object $LOCK = new Object[0];
    public static void hello() {
        synchronized ($LOCK) {
            System.out.println("world");
        }
    }
}
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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;
    }
}

// 相当于如下所示: 

import java.util.concurrent.atomic.AtomicReference;
public class GetterLazyExample {
    private final AtomicReference<java.lang.Object> cached = new AtomicReference<>();
    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;
    }
}
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@SupportedSourceVersion(SourceVersion.RELEASE_8)
@SupportedAnnotationTypes("com.alipay.kris.other.lombok.*")
public class MyAnnotaionProcessor extends AbstractProcessor {
    public MyAnnotaionProcessor() {
        super();
    }
    @Override
    public boolean process(Set<? extends TypeElement> annotations,RoundEnvironment roundEnv) {
        for (Element elem : roundEnv.getElementsAnnotatedWith(MyAnnotation.class)) {
            MyAnnotation annotation = elem.getAnnotation(MyAnnotation.class);
            String message = "annotation found in " + elem.getSimpleName()
                + " with  " + annotation.value();
            addToString(elem);
            processingEnv.getMessager().printMessage(Diagnostic.Kind.NOTE, message);
        }
        return true; // no further processing of this annotation type
    }
}