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15java语法糖与java编译器泛型与类型擦除桥接方法

admin 11月 12, 2020 0

也就是说，我们可以通过配置该参数，扩大 Integer 缓存的范围。Java 虚拟机参数 -XX:+AggressiveOpts 也会将 IntegerCache.high 调整至 20000。

泛型与类型擦除

桥接方法

public class <T extends  Number> {

  public void add(T number) {

  }
}
public class NumberS extends <Integer> {

  
  public void add(Integer number) {

  }

  
}

javap -v NumberS.class
Classfile /D:/workspace/demo/se-demo/src/main/java/brige/NumberS.class
  Last modified 2019-3-26; size 550 bytes
  MD5 checksum 5434bc6cbc8277ec249d44c992fe26bc
  Compiled from "NumberS.java"
public class brige.NumberS extends brige.NumberF<java.lang.Integer>
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   
   #2 = Class              #22            // java/lang/Integer
   #3 = Methodref          #4.#23         // brige/NumberS.add:(Ljava/lang/
Integer;)V
   #4 = Class              #24            // brige/NumberS
   #5 = Class              #25            // brige/NumberF
   #6 = Utf8               <init>
   #7 = Utf8               ()V
   #8 = Utf8               Code
   #9 = Utf8               LineNumberTable
  #10 = Utf8               add
  #11 = Utf8               (Ljava/lang/Integer;)V
  #12 = Utf8               foo
  #13 = Utf8               ([I)V
  #14 = Utf8               StackMapTable
  #15 = Class              #26            // "[I"
  #16 = Utf8               (Ljava/lang/Number;)V
  #17 = Utf8               Signature
  #18 = Utf8               Lbrige/NumberF<Ljava/lang/Integer;>;
  #19 = Utf8               SourceFile
  #20 = Utf8               NumberS.java
  #21 = NameAndType        #6:#7          // "<init>":()V
  #22 = Utf8               java/lang/Integer
  #23 = NameAndType        #10:#11        // add:(Ljava/lang/Integer;)V
  #24 = Utf8               brige/NumberS
  #25 = Utf8               brige/NumberF
  #26 = Utf8               [I
{
  public brige.NumberS();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1                  // Method brige/NumberF."<ini
t>":()V
         4: return
      LineNumberTable:
        line 16: 0

  public void add(java.lang.Integer);
    descriptor: (Ljava/lang/Integer;)V
    flags: ACC_PUBLIC
    Code:
      stack=0, locals=2, args_size=2
         0: return
      LineNumberTable:
        line 21: 0
  // 桥接方法
  public void add(java.lang.Number);
    descriptor: (Ljava/lang/Number;)V
    flags: ACC_PUBLIC, ACC_BRIDGE, ACC_SYNTHETIC
    Code:
      stack=2, locals=2, args_size=2
         0: aload_0
         1: aload_1
         2: checkcast     #2                  // class java/lang/Integer
         5: invokevirtual #3                  // Method add:(Ljava/lang/Int
eger;)V
         8: return
      LineNumberTable:
        line 16: 0
}
Signature: #18                          // Lbrige/NumberF<Ljava/lang/Intege
r;>;
SourceFile: "NumberS.java"