java lambda表达式是否有与之关联的on对象，以及为什么“this”不引用lambda表达式的对象？

5 月 Questions & Answers 79

我对是否存在与lambda表达式关联的对象感到非常困惑，因为有人说lambda表达式中的“this”并不是指lambda表达式的对象，因为lambda表达式没有任何对象，但又有人说如果lambda表达式没有捕获变量从作用域之外，相同的单例对象将用于lambda表达式的每次调用

现在，我假设将有一个对象与lambda表达式关联（我想这回答了我的第一个问题，如果我错了，请纠正我），所以我的问题是，那么为什么“this”不指lambda表达式的对象，就像在匿名类中发生的情况一样

更新： 我的3个测试班：

import java.util.function.Consumer;

public class LambdaByteCodeAnalysis1 {

    public static void main(String[] args) {
        testConsumer();
    }

    private static void testConsumer() {
        // *** void accept(T t); ***
        testConsumerImpl((value) -> System.out.println("Hello, Mr. " + value));

    }
    private static void testConsumerImpl(Consumer<Object> consumer) {
        consumer.accept("testConsumer");
    }

}


##############
import java.util.function.Consumer;

public class LambdaByteCodeAnalysis2 {

    public static void main(String[] args) {
        testConsumer();
    }

    private static void testConsumer() {
        int testing = 0;
        testConsumerImpl((value) -> {
            System.out.println("Hello, Mr. " + value);
            System.out.println(testing);
        });

    }
    private static void testConsumerImpl(Consumer<Object> consumer) {
        consumer.accept("testConsumer");
    }

}


################
import java.util.function.Consumer;

public class LambdaByteCodeAnalysis3 {

    int testing = 0;

    public static void main(String[] args) {
        testConsumer();
    }

    private static void testConsumer() {
        LambdaByteCodeAnalysis3 lambdaByteCodeAnalysis3 = new LambdaByteCodeAnalysis3();
        testConsumerImpl((value) -> {
            System.out.println("Hello, Mr. " + value);
            System.out.println(lambdaByteCodeAnalysis3.testing);
        });

    }
    private static void testConsumerImpl(Consumer<Object> consumer) {
        consumer.accept("testConsumer");
    }

}

现在，字节码的顺序相同：

LambdaByteCodeAnalysis1。班级

C:\E_Drive\Projects\SourceCode\Learning\learn\src\com\learn\oracle\LearningJavaLang\ClassesAndObject\LamdaExpression>javap -v LambdaByteCodeAnalysis1
Classfile /C:/E_Drive/Projects/SourceCode/Learning/learn/src/com/learn/oracle/LearningJavaLang/ClassesAndObject/LamdaExpression/LambdaByteCodeAnalysis1.class
  Last modified 15 Aug, 2018; size 1574 bytes
  MD5 checksum d90045ca82de96636d8fc91f54637c32
  Compiled from "LambdaByteCodeAnalysis1.java"
public class LambdaByteCodeAnalysis1
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref          #16.#32        // java/lang/Object."<init>":()V
   #2 = Methodref          #15.#33        // LambdaByteCodeAnalysis1.testConsumer:()V
   #3 = InvokeDynamic      #0:#38         // #0:accept:()Ljava/util/function/Consumer;
   #4 = Methodref          #15.#39        // LambdaByteCodeAnalysis1.testConsumerImpl:(Ljava/util/function/Consumer;)V
   #5 = String             #23            // testConsumer
   #6 = InterfaceMethodref #40.#41        // java/util/function/Consumer.accept:(Ljava/lang/Object;)V
   #7 = Fieldref           #42.#43        // java/lang/System.out:Ljava/io/PrintStream;
   #8 = Class              #44            // java/lang/StringBuilder
   #9 = Methodref          #8.#32         // java/lang/StringBuilder."<init>":()V
  #10 = String             #45            // Hello, Mr.
  #11 = Methodref          #8.#46         // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #12 = Methodref          #8.#47         // java/lang/StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
  #13 = Methodref          #8.#48         // java/lang/StringBuilder.toString:()Ljava/lang/String;
  #14 = Methodref          #49.#50        // java/io/PrintStream.println:(Ljava/lang/String;)V
  #15 = Class              #51            // LambdaByteCodeAnalysis1
  #16 = Class              #52            // java/lang/Object
  #17 = Utf8               <init>
  #18 = Utf8               ()V
  #19 = Utf8               Code
  #20 = Utf8               LineNumberTable
  #21 = Utf8               main
  #22 = Utf8               ([Ljava/lang/String;)V
  #23 = Utf8               testConsumer
  #24 = Utf8               testConsumerImpl
  #25 = Utf8               (Ljava/util/function/Consumer;)V
  #26 = Utf8               Signature
  #27 = Utf8               (Ljava/util/function/Consumer<Ljava/lang/Object;>;)V
  #28 = Utf8               lambda$testConsumer$0
  #29 = Utf8               (Ljava/lang/Object;)V
  #30 = Utf8               SourceFile
  #31 = Utf8               LambdaByteCodeAnalysis1.java
  #32 = NameAndType        #17:#18        // "<init>":()V
  #33 = NameAndType        #23:#18        // testConsumer:()V
  #34 = Utf8               BootstrapMethods
  #35 = MethodHandle       #6:#53         // invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/Stri
ng;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #36 = MethodType         #29            //  (Ljava/lang/Object;)V
  #37 = MethodHandle       #6:#54         // invokestatic LambdaByteCodeAnalysis1.lambda$testConsumer$0:(Ljava/lang/Object;)V
  #38 = NameAndType        #55:#56        // accept:()Ljava/util/function/Consumer;
  #39 = NameAndType        #24:#25        // testConsumerImpl:(Ljava/util/function/Consumer;)V
  #40 = Class              #57            // java/util/function/Consumer
  #41 = NameAndType        #55:#29        // accept:(Ljava/lang/Object;)V
  #42 = Class              #58            // java/lang/System
  #43 = NameAndType        #59:#60        // out:Ljava/io/PrintStream;
  #44 = Utf8               java/lang/StringBuilder
  #45 = Utf8               Hello, Mr.
  #46 = NameAndType        #61:#62        // append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #47 = NameAndType        #61:#63        // append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
  #48 = NameAndType        #64:#65        // toString:()Ljava/lang/String;
  #49 = Class              #66            // java/io/PrintStream
  #50 = NameAndType        #67:#68        // println:(Ljava/lang/String;)V
  #51 = Utf8               LambdaByteCodeAnalysis1
  #52 = Utf8               java/lang/Object
  #53 = Methodref          #69.#70        // java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang
/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #54 = Methodref          #15.#71        // LambdaByteCodeAnalysis1.lambda$testConsumer$0:(Ljava/lang/Object;)V
  #55 = Utf8               accept
  #56 = Utf8               ()Ljava/util/function/Consumer;
  #57 = Utf8               java/util/function/Consumer
  #58 = Utf8               java/lang/System
  #59 = Utf8               out
  #60 = Utf8               Ljava/io/PrintStream;
  #61 = Utf8               append
  #62 = Utf8               (Ljava/lang/String;)Ljava/lang/StringBuilder;
  #63 = Utf8               (Ljava/lang/Object;)Ljava/lang/StringBuilder;
  #64 = Utf8               toString
  #65 = Utf8               ()Ljava/lang/String;
  #66 = Utf8               java/io/PrintStream
  #67 = Utf8               println
  #68 = Utf8               (Ljava/lang/String;)V
  #69 = Class              #72            // java/lang/invoke/LambdaMetafactory
  #70 = NameAndType        #73:#77        // metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invok
e/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #71 = NameAndType        #28:#29        // lambda$testConsumer$0:(Ljava/lang/Object;)V
  #72 = Utf8               java/lang/invoke/LambdaMetafactory
  #73 = Utf8               metafactory
  #74 = Class              #79            // java/lang/invoke/MethodHandles$Lookup
  #75 = Utf8               Lookup
  #76 = Utf8               InnerClasses
  #77 = Utf8               (Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke
/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #78 = Class              #80            // java/lang/invoke/MethodHandles
  #79 = Utf8               java/lang/invoke/MethodHandles$Lookup
  #80 = Utf8               java/lang/invoke/MethodHandles
{
  public LambdaByteCodeAnalysis1();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1                  // Method java/lang/Object."<init>":()V
         4: return
      LineNumberTable:
        line 3: 0

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=0, locals=1, args_size=1
         0: invokestatic  #2                  // Method testConsumer:()V
         3: return
      LineNumberTable:
        line 6: 0
        line 7: 3
}
SourceFile: "LambdaByteCodeAnalysis1.java"
InnerClasses:
     public static final #75= #74 of #78; //Lookup=class java/lang/invoke/MethodHandles$Lookup of class java/lang/invoke/MethodHandles
BootstrapMethods:
  0: #35 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljav
a/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
    Method arguments:
      #36 (Ljava/lang/Object;)V
      #37 invokestatic LambdaByteCodeAnalysis1.lambda$testConsumer$0:(Ljava/lang/Object;)V
      #36 (Ljava/lang/Object;)V

C:\E_Drive\Projects\SourceCode\Learning\learn\src\com\learn\oracle\LearningJavaLang\ClassesAndObject\LamdaExpression>

LambdaByteCodeAnalysis2。班级

C:\E_Drive\Projects\SourceCode\Learning\learn\src\com\learn\oracle\LearningJavaLang\ClassesAndObject\LamdaExpression>javap -v LambdaByteCodeAnalysis2
Classfile /C:/E_Drive/Projects/SourceCode/Learning/learn/src/com/learn/oracle/LearningJavaLang/ClassesAndObject/LamdaExpression/LambdaByteCodeAnalysis2.class
  Last modified 15 Aug, 2018; size 1639 bytes
  MD5 checksum 7e61b6b121ba9d8097f4034f331df1c9
  Compiled from "LambdaByteCodeAnalysis2.java"
public class LambdaByteCodeAnalysis2
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref          #17.#33        // java/lang/Object."<init>":()V
   #2 = Methodref          #16.#34        // LambdaByteCodeAnalysis2.testConsumer:()V
   #3 = InvokeDynamic      #0:#39         // #0:accept:(I)Ljava/util/function/Consumer;
   #4 = Methodref          #16.#40        // LambdaByteCodeAnalysis2.testConsumerImpl:(Ljava/util/function/Consumer;)V
   #5 = String             #24            // testConsumer
   #6 = InterfaceMethodref #41.#42        // java/util/function/Consumer.accept:(Ljava/lang/Object;)V
   #7 = Fieldref           #43.#44        // java/lang/System.out:Ljava/io/PrintStream;
   #8 = Class              #45            // java/lang/StringBuilder
   #9 = Methodref          #8.#33         // java/lang/StringBuilder."<init>":()V
  #10 = String             #46            // Hello, Mr.
  #11 = Methodref          #8.#47         // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #12 = Methodref          #8.#48         // java/lang/StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
  #13 = Methodref          #8.#49         // java/lang/StringBuilder.toString:()Ljava/lang/String;
  #14 = Methodref          #50.#51        // java/io/PrintStream.println:(Ljava/lang/String;)V
  #15 = Methodref          #50.#52        // java/io/PrintStream.println:(I)V
  #16 = Class              #53            // LambdaByteCodeAnalysis2
  #17 = Class              #54            // java/lang/Object
  #18 = Utf8               <init>
  #19 = Utf8               ()V
  #20 = Utf8               Code
  #21 = Utf8               LineNumberTable
  #22 = Utf8               main
  #23 = Utf8               ([Ljava/lang/String;)V
  #24 = Utf8               testConsumer
  #25 = Utf8               testConsumerImpl
  #26 = Utf8               (Ljava/util/function/Consumer;)V
  #27 = Utf8               Signature
  #28 = Utf8               (Ljava/util/function/Consumer<Ljava/lang/Object;>;)V
  #29 = Utf8               lambda$testConsumer$0
  #30 = Utf8               (ILjava/lang/Object;)V
  #31 = Utf8               SourceFile
  #32 = Utf8               LambdaByteCodeAnalysis2.java
  #33 = NameAndType        #18:#19        // "<init>":()V
  #34 = NameAndType        #24:#19        // testConsumer:()V
  #35 = Utf8               BootstrapMethods
  #36 = MethodHandle       #6:#55         // invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/Stri
ng;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #37 = MethodType         #56            //  (Ljava/lang/Object;)V
  #38 = MethodHandle       #6:#57         // invokestatic LambdaByteCodeAnalysis2.lambda$testConsumer$0:(ILjava/lang/Object;)V
  #39 = NameAndType        #58:#59        // accept:(I)Ljava/util/function/Consumer;
  #40 = NameAndType        #25:#26        // testConsumerImpl:(Ljava/util/function/Consumer;)V
  #41 = Class              #60            // java/util/function/Consumer
  #42 = NameAndType        #58:#56        // accept:(Ljava/lang/Object;)V
  #43 = Class              #61            // java/lang/System
  #44 = NameAndType        #62:#63        // out:Ljava/io/PrintStream;
  #45 = Utf8               java/lang/StringBuilder
  #46 = Utf8               Hello, Mr.
  #47 = NameAndType        #64:#65        // append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #48 = NameAndType        #64:#66        // append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
  #49 = NameAndType        #67:#68        // toString:()Ljava/lang/String;
  #50 = Class              #69            // java/io/PrintStream
  #51 = NameAndType        #70:#71        // println:(Ljava/lang/String;)V
  #52 = NameAndType        #70:#72        // println:(I)V
  #53 = Utf8               LambdaByteCodeAnalysis2
  #54 = Utf8               java/lang/Object
  #55 = Methodref          #73.#74        // java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang
/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #56 = Utf8               (Ljava/lang/Object;)V
  #57 = Methodref          #16.#75        // LambdaByteCodeAnalysis2.lambda$testConsumer$0:(ILjava/lang/Object;)V
  #58 = Utf8               accept
  #59 = Utf8               (I)Ljava/util/function/Consumer;
  #60 = Utf8               java/util/function/Consumer
  #61 = Utf8               java/lang/System
  #62 = Utf8               out
  #63 = Utf8               Ljava/io/PrintStream;
  #64 = Utf8               append
  #65 = Utf8               (Ljava/lang/String;)Ljava/lang/StringBuilder;
  #66 = Utf8               (Ljava/lang/Object;)Ljava/lang/StringBuilder;
  #67 = Utf8               toString
  #68 = Utf8               ()Ljava/lang/String;
  #69 = Utf8               java/io/PrintStream
  #70 = Utf8               println
  #71 = Utf8               (Ljava/lang/String;)V
  #72 = Utf8               (I)V
  #73 = Class              #76            // java/lang/invoke/LambdaMetafactory
  #74 = NameAndType        #77:#81        // metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invok
e/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #75 = NameAndType        #29:#30        // lambda$testConsumer$0:(ILjava/lang/Object;)V
  #76 = Utf8               java/lang/invoke/LambdaMetafactory
  #77 = Utf8               metafactory
  #78 = Class              #83            // java/lang/invoke/MethodHandles$Lookup
  #79 = Utf8               Lookup
  #80 = Utf8               InnerClasses
  #81 = Utf8               (Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke
/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #82 = Class              #84            // java/lang/invoke/MethodHandles
  #83 = Utf8               java/lang/invoke/MethodHandles$Lookup
  #84 = Utf8               java/lang/invoke/MethodHandles
{
  public LambdaByteCodeAnalysis2();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1                  // Method java/lang/Object."<init>":()V
         4: return
      LineNumberTable:
        line 3: 0

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=0, locals=1, args_size=1
         0: invokestatic  #2                  // Method testConsumer:()V
         3: return
      LineNumberTable:
        line 6: 0
        line 7: 3
}
SourceFile: "LambdaByteCodeAnalysis2.java"
InnerClasses:
     public static final #79= #78 of #82; //Lookup=class java/lang/invoke/MethodHandles$Lookup of class java/lang/invoke/MethodHandles
BootstrapMethods:
  0: #36 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljav
a/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
    Method arguments:
      #37 (Ljava/lang/Object;)V
      #38 invokestatic LambdaByteCodeAnalysis2.lambda$testConsumer$0:(ILjava/lang/Object;)V
      #37 (Ljava/lang/Object;)V

C:\E_Drive\Projects\SourceCode\Learning\learn\src\com\learn\oracle\LearningJavaLang\ClassesAndObject\LamdaExpression>

LambdaByteCodeAnalysis3。班级

C:\E_Drive\Projects\SourceCode\Learning\learn\src\com\learn\oracle\LearningJavaLang\ClassesAndObject\LamdaExpression>javap -v LambdaByteCodeAnalysis3
Classfile /C:/E_Drive/Projects/SourceCode/Learning/learn/src/com/learn/oracle/LearningJavaLang/ClassesAndObject/LamdaExpression/LambdaByteCodeAnalysis3.class
  Last modified 15 Aug, 2018; size 1742 bytes
  MD5 checksum 18bf579a4a95e700e29ec7e35bbac1b4
  Compiled from "LambdaByteCodeAnalysis3.java"
public class LambdaByteCodeAnalysis3
  minor version: 0
  major version: 52
  flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
   #1 = Methodref          #19.#37        // java/lang/Object."<init>":()V
   #2 = Fieldref           #4.#38         // LambdaByteCodeAnalysis3.testing:I
   #3 = Methodref          #4.#39         // LambdaByteCodeAnalysis3.testConsumer:()V
   #4 = Class              #40            // LambdaByteCodeAnalysis3
   #5 = Methodref          #4.#37         // LambdaByteCodeAnalysis3."<init>":()V
   #6 = InvokeDynamic      #0:#45         // #0:accept:(LLambdaByteCodeAnalysis3;)Ljava/util/function/Consumer;
   #7 = Methodref          #4.#46         // LambdaByteCodeAnalysis3.testConsumerImpl:(Ljava/util/function/Consumer;)V
   #8 = String             #28            // testConsumer
   #9 = InterfaceMethodref #47.#48        // java/util/function/Consumer.accept:(Ljava/lang/Object;)V
  #10 = Fieldref           #49.#50        // java/lang/System.out:Ljava/io/PrintStream;
  #11 = Class              #51            // java/lang/StringBuilder
  #12 = Methodref          #11.#37        // java/lang/StringBuilder."<init>":()V
  #13 = String             #52            // Hello, Mr.
  #14 = Methodref          #11.#53        // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #15 = Methodref          #11.#54        // java/lang/StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
  #16 = Methodref          #11.#55        // java/lang/StringBuilder.toString:()Ljava/lang/String;
  #17 = Methodref          #56.#57        // java/io/PrintStream.println:(Ljava/lang/String;)V
  #18 = Methodref          #56.#58        // java/io/PrintStream.println:(I)V
  #19 = Class              #59            // java/lang/Object
  #20 = Utf8               testing
  #21 = Utf8               I
  #22 = Utf8               <init>
  #23 = Utf8               ()V
  #24 = Utf8               Code
  #25 = Utf8               LineNumberTable
  #26 = Utf8               main
  #27 = Utf8               ([Ljava/lang/String;)V
  #28 = Utf8               testConsumer
  #29 = Utf8               testConsumerImpl
  #30 = Utf8               (Ljava/util/function/Consumer;)V
  #31 = Utf8               Signature
  #32 = Utf8               (Ljava/util/function/Consumer<Ljava/lang/Object;>;)V
  #33 = Utf8               lambda$testConsumer$0
  #34 = Utf8               (LLambdaByteCodeAnalysis3;Ljava/lang/Object;)V
  #35 = Utf8               SourceFile
  #36 = Utf8               LambdaByteCodeAnalysis3.java
  #37 = NameAndType        #22:#23        // "<init>":()V
  #38 = NameAndType        #20:#21        // testing:I
  #39 = NameAndType        #28:#23        // testConsumer:()V
  #40 = Utf8               LambdaByteCodeAnalysis3
  #41 = Utf8               BootstrapMethods
  #42 = MethodHandle       #6:#60         // invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/Stri
ng;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #43 = MethodType         #61            //  (Ljava/lang/Object;)V
  #44 = MethodHandle       #6:#62         // invokestatic LambdaByteCodeAnalysis3.lambda$testConsumer$0:(LLambdaByteCodeAnalysis3;Ljava/lang/Object;)V
  #45 = NameAndType        #63:#64        // accept:(LLambdaByteCodeAnalysis3;)Ljava/util/function/Consumer;
  #46 = NameAndType        #29:#30        // testConsumerImpl:(Ljava/util/function/Consumer;)V
  #47 = Class              #65            // java/util/function/Consumer
  #48 = NameAndType        #63:#61        // accept:(Ljava/lang/Object;)V
  #49 = Class              #66            // java/lang/System
  #50 = NameAndType        #67:#68        // out:Ljava/io/PrintStream;
  #51 = Utf8               java/lang/StringBuilder
  #52 = Utf8               Hello, Mr.
  #53 = NameAndType        #69:#70        // append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
  #54 = NameAndType        #69:#71        // append:(Ljava/lang/Object;)Ljava/lang/StringBuilder;
  #55 = NameAndType        #72:#73        // toString:()Ljava/lang/String;
  #56 = Class              #74            // java/io/PrintStream
  #57 = NameAndType        #75:#76        // println:(Ljava/lang/String;)V
  #58 = NameAndType        #75:#77        // println:(I)V
  #59 = Utf8               java/lang/Object
  #60 = Methodref          #78.#79        // java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang
/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #61 = Utf8               (Ljava/lang/Object;)V
  #62 = Methodref          #4.#80         // LambdaByteCodeAnalysis3.lambda$testConsumer$0:(LLambdaByteCodeAnalysis3;Ljava/lang/Object;)V
  #63 = Utf8               accept
  #64 = Utf8               (LLambdaByteCodeAnalysis3;)Ljava/util/function/Consumer;
  #65 = Utf8               java/util/function/Consumer
  #66 = Utf8               java/lang/System
  #67 = Utf8               out
  #68 = Utf8               Ljava/io/PrintStream;
  #69 = Utf8               append
  #70 = Utf8               (Ljava/lang/String;)Ljava/lang/StringBuilder;
  #71 = Utf8               (Ljava/lang/Object;)Ljava/lang/StringBuilder;
  #72 = Utf8               toString
  #73 = Utf8               ()Ljava/lang/String;
  #74 = Utf8               java/io/PrintStream
  #75 = Utf8               println
  #76 = Utf8               (Ljava/lang/String;)V
  #77 = Utf8               (I)V
  #78 = Class              #81            // java/lang/invoke/LambdaMetafactory
  #79 = NameAndType        #82:#86        // metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invok
e/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #80 = NameAndType        #33:#34        // lambda$testConsumer$0:(LLambdaByteCodeAnalysis3;Ljava/lang/Object;)V
  #81 = Utf8               java/lang/invoke/LambdaMetafactory
  #82 = Utf8               metafactory
  #83 = Class              #88            // java/lang/invoke/MethodHandles$Lookup
  #84 = Utf8               Lookup
  #85 = Utf8               InnerClasses
  #86 = Utf8               (Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke
/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
  #87 = Class              #89            // java/lang/invoke/MethodHandles
  #88 = Utf8               java/lang/invoke/MethodHandles$Lookup
  #89 = Utf8               java/lang/invoke/MethodHandles
{
  int testing;
    descriptor: I
    flags:

  public LambdaByteCodeAnalysis3();
    descriptor: ()V
    flags: ACC_PUBLIC
    Code:
      stack=2, locals=1, args_size=1
         0: aload_0
         1: invokespecial #1                  // Method java/lang/Object."<init>":()V
         4: aload_0
         5: iconst_0
         6: putfield      #2                  // Field testing:I
         9: return
      LineNumberTable:
        line 3: 0
        line 5: 4

  public static void main(java.lang.String[]);
    descriptor: ([Ljava/lang/String;)V
    flags: ACC_PUBLIC, ACC_STATIC
    Code:
      stack=0, locals=1, args_size=1
         0: invokestatic  #3                  // Method testConsumer:()V
         3: return
      LineNumberTable:
        line 8: 0
        line 9: 3
}
SourceFile: "LambdaByteCodeAnalysis3.java"
InnerClasses:
     public static final #84= #83 of #87; //Lookup=class java/lang/invoke/MethodHandles$Lookup of class java/lang/invoke/MethodHandles
BootstrapMethods:
  0: #42 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljav
a/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
    Method arguments:
      #43 (Ljava/lang/Object;)V
      #44 invokestatic LambdaByteCodeAnalysis3.lambda$testConsumer$0:(LLambdaByteCodeAnalysis3;Ljava/lang/Object;)V
      #43 (Ljava/lang/Object;)V

C:\E_Drive\Projects\SourceCode\Learning\learn\src\com\learn\oracle\LearningJavaLang\ClassesAndObject\LamdaExpression>

共 (2) 个答案

# 1 楼答案

我的答案和简单的逻辑是，因为this用于引用对象的状态，而lambda表达式没有任何状态（也捕获了外部变量访问），所以this引用lambda表达式的对象没有意义
# 2 楼答案

报告说：

Unlike code appearing in anonymous class declarations, the meaning of names and the this and super keywords appearing in a lambda body, along with the accessibility of referenced declarations, are the same as in the surrounding context (except that lambda parameters introduce new names).

The transparency of this (both explicit and implicit) in the body of a lambda expression - that is, treating it the same as in the surrounding context - allows more flexibility for implementations, and prevents the meaning of unqualified names in the body from being dependent on overload resolution.

Practically speaking, it is unusual for a lambda expression to need to talk about itself (either to call itself recursively or to invoke its other methods), while it is more common to want to use names to refer to things in the enclosing class that would otherwise be shadowed (this, toString()). If it is necessary for a lambda expression to refer to itself (as if via this), a method reference or an anonymous inner class should be used instead.

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有 Java 编程相关的问题?

java lambda表达式是否有与之关联的on对象，以及为什么“this”不引用lambda表达式的对象？

共 (2) 个答案

# 1 楼答案

# 2 楼答案