Java Bridge Method

1.java桥接方法

import java.lang.reflect.Method;
import java.util.Arrays;

public class TestBridgeMethod {
    public static class Warehouse<T>{
        public T getValue() {
            return value;
        }
        public void setValue(T value) {
            this.value = value;
        }
        private T value;
    }

    public static class WarehouseInteger extends Warehouse<Integer>{
        @Override
        public void setValue(Integer value) {
            super.setValue(value);
        }
    }

    public static void main(String[] args) throws InterruptedException {
        Method[] declaredMethods = WarehouseInteger.class.getDeclaredMethods();
        Arrays.asList(declaredMethods).forEach((value)->{
            System.out.println(value);
        });
        Thread.sleep(Integer.MAX_VALUE);
    }
}

结果显示:
public void TestBridgeMethod$WarehouseInteger.setValue(java.lang.Integer)
public void TestBridgeMethod$WarehouseInteger.setValue(java.lang.Object)

使用javap -c 查看class文件:

Compiled from "TestBridgeMethod.java"
public class TestBridgeMethod$Warehouse<T> {
  public TestBridgeMethod$Warehouse();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method java/lang/Object."<init>":()V
       4: return

  public T getValue();
    Code:
       0: aload_0
       1: getfield      #2                  // Field value:Ljava/lang/Object;
       4: areturn

  public void setValue(T);
    Code:
       0: aload_0
       1: aload_1
       2: putfield      #2                  // Field value:Ljava/lang/Object;
       5: return
}

Compiled from "TestBridgeMethod.java"
public class TestBridgeMethod$WarehouseInteger extends TestBridgeMethod$Warehouse<java.lang.Integer> {
  public TestBridgeMethod$WarehouseInteger();
    Code:
       0: aload_0
       1: invokespecial #1                  // Method TestBridgeMethod$Warehouse."<init>":()V
       4: return

  public void setValue(java.lang.Integer);
    Code:
       0: aload_0
       1: aload_1
       2: invokespecial #2                  // Method TestBridgeMethod$Warehouse.setValue:(Ljava/lang/Object;)V
       5: return

  public void setValue(java.lang.Object);
    Code:
       0: aload_0
       1: aload_1
       2: checkcast     #3                  // class java/lang/Integer
       5: invokevirtual #4                  // Method setValue:(Ljava/lang/Integer;)V
       8: return
}

在TestBridgeMethod$WarehouseInteger类中setValue:(Ljava/lang/Object;)V中调用了本类的setValue:(Ljava/lang/Integer;)V,该方法为编译器帮我们生成的桥接方法