字节码分析-Lambda表达式
源码
package java.bytecode;
import java.util.function.Function;
import java.util.function.Predicate;
/**
* Lambda表达式示例 - 演示Java 8 Lambda表达式
*/
public class LambdaExample {
// Lambda表达式示例
public void lambdaExample() {
Function<String, Integer> func = s -> s.length();
int length = func.apply("Hello");
System.out.println("Length: " + length);
}
// Lambda表达式 - 多行
public void lambdaMultiLineExample() {
Function<String, String> func = s -> {
String upper = s.toUpperCase();
return upper + "!";
};
String result = func.apply("hello");
System.out.println(result);
}
// Lambda表达式 - Predicate
public void lambdaPredicateExample() {
Predicate<Integer> isEven = n -> n % 2 == 0;
boolean result = isEven.test(10);
System.out.println("Is 10 even? " + result);
}
}
结构化反解析
Classfile /D:/zcp/github/yggdrasil/java/bytecode/LambdaExample.class
Last modified 2025-12-3; size 2289 bytes
MD5 checksum 27bce9a64729abd62aadd3d8a9346099
Compiled from "LambdaExample.java"
public class java.bytecode.LambdaExample
minor version: 0
major version: 52
flags: ACC_PUBLIC, ACC_SUPER
Constant pool:
#1 = Methodref #2.#3 // java/lang/Object."<init>":()V
#2 = Class #4 // java/lang/Object
#3 = NameAndType #5:#6 // "<init>":()V
#4 = Utf8 java/lang/Object
#5 = Utf8 <init>
#6 = Utf8 ()V
#7 = InvokeDynamic #0:#8 // #0:apply:()Ljava/util/function/Function;
#8 = NameAndType #9:#10 // apply:()Ljava/util/function/Function;
#9 = Utf8 apply
#10 = Utf8 ()Ljava/util/function/Function;
#11 = String #12 // Hello
#12 = Utf8 Hello
#13 = InterfaceMethodref #14.#15 // java/util/function/Function.apply:(Ljava/lang/Object;)Ljava/lang/Object;
#14 = Class #16 // java/util/function/Function
#15 = NameAndType #9:#17 // apply:(Ljava/lang/Object;)Ljava/lang/Object;
#16 = Utf8 java/util/function/Function
#17 = Utf8 (Ljava/lang/Object;)Ljava/lang/Object;
#18 = Class #19 // java/lang/Integer
#19 = Utf8 java/lang/Integer
#20 = Methodref #18.#21 // java/lang/Integer.intValue:()I
#21 = NameAndType #22:#23 // intValue:()I
#22 = Utf8 intValue
#23 = Utf8 ()I
#24 = Fieldref #25.#26 // java/lang/System.out:Ljava/io/PrintStream;
#25 = Class #27 // java/lang/System
#26 = NameAndType #28:#29 // out:Ljava/io/PrintStream;
#27 = Utf8 java/lang/System
#28 = Utf8 out
#29 = Utf8 Ljava/io/PrintStream;
#30 = Class #31 // java/lang/StringBuilder
#31 = Utf8 java/lang/StringBuilder
#32 = Methodref #30.#3 // java/lang/StringBuilder."<init>":()V
#33 = String #34 // Length:
#34 = Utf8 Length:
#35 = Methodref #30.#36 // java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
#36 = NameAndType #37:#38 // append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
#37 = Utf8 append
#38 = Utf8 (Ljava/lang/String;)Ljava/lang/StringBuilder;
#39 = Methodref #30.#40 // java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
#40 = NameAndType #37:#41 // append:(I)Ljava/lang/StringBuilder;
#41 = Utf8 (I)Ljava/lang/StringBuilder;
#42 = Methodref #30.#43 // java/lang/StringBuilder.toString:()Ljava/lang/String;
#43 = NameAndType #44:#45 // toString:()Ljava/lang/String;
#44 = Utf8 toString
#45 = Utf8 ()Ljava/lang/String;
#46 = Methodref #47.#48 // java/io/PrintStream.println:(Ljava/lang/String;)V
#47 = Class #49 // java/io/PrintStream
#48 = NameAndType #50:#51 // println:(Ljava/lang/String;)V
#49 = Utf8 java/io/PrintStream
#50 = Utf8 println
#51 = Utf8 (Ljava/lang/String;)V
#52 = InvokeDynamic #1:#8 // #1:apply:()Ljava/util/function/Function;
#53 = String #54 // hello
#54 = Utf8 hello
#55 = Class #56 // java/lang/String
#56 = Utf8 java/lang/String
#57 = InvokeDynamic #2:#58 // #2:test:()Ljava/util/function/Predicate;
#58 = NameAndType #59:#60 // test:()Ljava/util/function/Predicate;
#59 = Utf8 test
#60 = Utf8 ()Ljava/util/function/Predicate;
#61 = Methodref #18.#62 // java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
#62 = NameAndType #63:#64 // valueOf:(I)Ljava/lang/Integer;
#63 = Utf8 valueOf
#64 = Utf8 (I)Ljava/lang/Integer;
#65 = InterfaceMethodref #66.#67 // java/util/function/Predicate.test:(Ljava/lang/Object;)Z
#66 = Class #68 // java/util/function/Predicate
#67 = NameAndType #59:#69 // test:(Ljava/lang/Object;)Z
#68 = Utf8 java/util/function/Predicate
#69 = Utf8 (Ljava/lang/Object;)Z
#70 = String #71 // Is 10 even?
#71 = Utf8 Is 10 even?
#72 = Methodref #30.#73 // java/lang/StringBuilder.append:(Z)Ljava/lang/StringBuilder;
#73 = NameAndType #37:#74 // append:(Z)Ljava/lang/StringBuilder;
#74 = Utf8 (Z)Ljava/lang/StringBuilder;
#75 = Methodref #55.#76 // java/lang/String.toUpperCase:()Ljava/lang/String;
#76 = NameAndType #77:#45 // toUpperCase:()Ljava/lang/String;
#77 = Utf8 toUpperCase
#78 = String #79 // !
#79 = Utf8 !
#80 = Methodref #55.#81 // java/lang/String.length:()I
#81 = NameAndType #82:#23 // length:()I
#82 = Utf8 length
#83 = Class #84 // java/bytecode/LambdaExample
#84 = Utf8 java/bytecode/LambdaExample
#85 = Utf8 Code
#86 = Utf8 LineNumberTable
#87 = Utf8 lambdaExample
#88 = Utf8 lambdaMultiLineExample
#89 = Utf8 lambdaPredicateExample
#90 = Utf8 lambda$lambdaPredicateExample$0
#91 = Utf8 (Ljava/lang/Integer;)Z
#92 = Utf8 StackMapTable
#93 = Utf8 lambda$lambdaMultiLineExample$0
#94 = Utf8 (Ljava/lang/String;)Ljava/lang/String;
#95 = Utf8 lambda$lambdaExample$0
#96 = Utf8 (Ljava/lang/String;)Ljava/lang/Integer;
#97 = Utf8 SourceFile
#98 = Utf8 LambdaExample.java
#99 = Utf8 BootstrapMethods
#100 = MethodType #17 // (Ljava/lang/Object;)Ljava/lang/Object;
#101 = MethodHandle #6:#102 // invokestatic java/bytecode/LambdaExample.lambda$lambdaExample$0:(Ljava/lang/String;)Ljava/lang/Integer;
#102 = Methodref #83.#103 // java/bytecode/LambdaExample.lambda$lambdaExample$0:(Ljava/lang/String;)Ljava/lang/Integer;
#103 = NameAndType #95:#96 // lambda$lambdaExample$0:(Ljava/lang/String;)Ljava/lang/Integer;
#104 = MethodType #96 // (Ljava/lang/String;)Ljava/lang/Integer;
#105 = MethodHandle #6:#106 // invokestatic java/bytecode/LambdaExample.lambda$lambdaMultiLineExample$0:(Ljava/lang/String;)Ljava/lang/String;
#106 = Methodref #83.#107 // java/bytecode/LambdaExample.lambda$lambdaMultiLineExample$0:(Ljava/lang/String;)Ljava/lang/String;
#107 = NameAndType #93:#94 // lambda$lambdaMultiLineExample$0:(Ljava/lang/String;)Ljava/lang/String;
#108 = MethodType #94 // (Ljava/lang/String;)Ljava/lang/String;
#109 = MethodType #69 // (Ljava/lang/Object;)Z
#110 = MethodHandle #6:#111 // invokestatic java/bytecode/LambdaExample.lambda$lambdaPredicateExample$0:(Ljava/lang/Integer;)Z
#111 = Methodref #83.#112 // java/bytecode/LambdaExample.lambda$lambdaPredicateExample$0:(Ljava/lang/Integer;)Z
#112 = NameAndType #90:#91 // lambda$lambdaPredicateExample$0:(Ljava/lang/Integer;)Z
#113 = MethodType #91 // (Ljava/lang/Integer;)Z
#114 = MethodHandle #6:#115 // invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
#115 = Methodref #116.#117 // java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
#116 = Class #118 // java/lang/invoke/LambdaMetafactory
#117 = NameAndType #119:#120 // metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
#118 = Utf8 java/lang/invoke/LambdaMetafactory
#119 = Utf8 metafactory
#120 = Utf8 (Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
#121 = Utf8 InnerClasses
#122 = Class #123 // java/lang/invoke/MethodHandles$Lookup
#123 = Utf8 java/lang/invoke/MethodHandles$Lookup
#124 = Class #125 // java/lang/invoke/MethodHandles
#125 = Utf8 java/lang/invoke/MethodHandles
#126 = Utf8 Lookup
{
public java.bytecode.LambdaExample();
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 9: 0
public void lambdaExample();
descriptor: ()V
flags: ACC_PUBLIC
Code:
stack=3, locals=3, args_size=1
0: invokedynamic #7, 0 // InvokeDynamic #0:apply:()Ljava/util/function/Function;
5: astore_1
6: aload_1
7: ldc #11 // String Hello
9: invokeinterface #13, 2 // InterfaceMethod java/util/function/Function.apply:(Ljava/lang/Object;)Ljava/lang/Object;
14: checkcast #18 // class java/lang/Integer
17: invokevirtual #20 // Method java/lang/Integer.intValue:()I
20: istore_2
21: getstatic #24 // Field java/lang/System.out:Ljava/io/PrintStream;
24: new #30 // class java/lang/StringBuilder
27: dup
28: invokespecial #32 // Method java/lang/StringBuilder."<init>":()V
31: ldc #33 // String Length:
33: invokevirtual #35 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
36: iload_2
37: invokevirtual #39 // Method java/lang/StringBuilder.append:(I)Ljava/lang/StringBuilder;
40: invokevirtual #42 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
43: invokevirtual #46 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
46: return
LineNumberTable:
line 13: 0
line 14: 6
line 15: 21
line 16: 46
public void lambdaMultiLineExample();
descriptor: ()V
flags: ACC_PUBLIC
Code:
stack=2, locals=3, args_size=1
0: invokedynamic #52, 0 // InvokeDynamic #1:apply:()Ljava/util/function/Function;
5: astore_1
6: aload_1
7: ldc #53 // String hello
9: invokeinterface #13, 2 // InterfaceMethod java/util/function/Function.apply:(Ljava/lang/Object;)Ljava/lang/Object;
14: checkcast #55 // class java/lang/String
17: astore_2
18: getstatic #24 // Field java/lang/System.out:Ljava/io/PrintStream;
21: aload_2
22: invokevirtual #46 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
25: return
LineNumberTable:
line 20: 0
line 24: 6
line 25: 18
line 26: 25
public void lambdaPredicateExample();
descriptor: ()V
flags: ACC_PUBLIC
Code:
stack=3, locals=3, args_size=1
0: invokedynamic #57, 0 // InvokeDynamic #2:test:()Ljava/util/function/Predicate;
5: astore_1
6: aload_1
7: bipush 10
9: invokestatic #61 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
12: invokeinterface #65, 2 // InterfaceMethod java/util/function/Predicate.test:(Ljava/lang/Object;)Z
17: istore_2
18: getstatic #24 // Field java/lang/System.out:Ljava/io/PrintStream;
21: new #30 // class java/lang/StringBuilder
24: dup
25: invokespecial #32 // Method java/lang/StringBuilder."<init>":()V
28: ldc #70 // String Is 10 even?
30: invokevirtual #35 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
33: iload_2
34: invokevirtual #72 // Method java/lang/StringBuilder.append:(Z)Ljava/lang/StringBuilder;
37: invokevirtual #42 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
40: invokevirtual #46 // Method java/io/PrintStream.println:(Ljava/lang/String;)V
43: return
LineNumberTable:
line 30: 0
line 31: 6
line 32: 18
line 33: 43
private static boolean lambda$lambdaPredicateExample$0(java.lang.Integer);
descriptor: (Ljava/lang/Integer;)Z
flags: ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
Code:
stack=2, locals=1, args_size=1
0: aload_0
1: invokevirtual #20 // Method java/lang/Integer.intValue:()I
4: iconst_2
5: irem
6: ifne 13
9: iconst_1
10: goto 14
13: iconst_0
14: ireturn
LineNumberTable:
line 30: 0
StackMapTable: number_of_entries = 2
frame_type = 13 /* same */
frame_type = 64 /* same_locals_1_stack_item */
stack = [ int ]
private static java.lang.String lambda$lambdaMultiLineExample$0(java.lang.String);
descriptor: (Ljava/lang/String;)Ljava/lang/String;
flags: ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
Code:
stack=2, locals=2, args_size=1
0: aload_0
1: invokevirtual #75 // Method java/lang/String.toUpperCase:()Ljava/lang/String;
4: astore_1
5: new #30 // class java/lang/StringBuilder
8: dup
9: invokespecial #32 // Method java/lang/StringBuilder."<init>":()V
12: aload_1
13: invokevirtual #35 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
16: ldc #78 // String !
18: invokevirtual #35 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;
21: invokevirtual #42 // Method java/lang/StringBuilder.toString:()Ljava/lang/String;
24: areturn
LineNumberTable:
line 21: 0
line 22: 5
private static java.lang.Integer lambda$lambdaExample$0(java.lang.String);
descriptor: (Ljava/lang/String;)Ljava/lang/Integer;
flags: ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
Code:
stack=1, locals=1, args_size=1
0: aload_0
1: invokevirtual #80 // Method java/lang/String.length:()I
4: invokestatic #61 // Method java/lang/Integer.valueOf:(I)Ljava/lang/Integer;
7: areturn
LineNumberTable:
line 13: 0
}
SourceFile: "LambdaExample.java"
BootstrapMethods:
0: #114 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
Method arguments:
#100 (Ljava/lang/Object;)Ljava/lang/Object;
#101 invokestatic java/bytecode/LambdaExample.lambda$lambdaExample$0:(Ljava/lang/String;)Ljava/lang/Integer;
#104 (Ljava/lang/String;)Ljava/lang/Integer;
1: #114 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
Method arguments:
#100 (Ljava/lang/Object;)Ljava/lang/Object;
#105 invokestatic java/bytecode/LambdaExample.lambda$lambdaMultiLineExample$0:(Ljava/lang/String;)Ljava/lang/String;
#108 (Ljava/lang/String;)Ljava/lang/String;
2: #114 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
Method arguments:
#109 (Ljava/lang/Object;)Z
#110 invokestatic java/bytecode/LambdaExample.lambda$lambdaPredicateExample$0:(Ljava/lang/Integer;)Z
#113 (Ljava/lang/Integer;)Z
InnerClasses:
public static final #126= #122 of #124; //Lookup=class java/lang/invoke/MethodHandles$Lookup of class java/lang/invoke/MethodHandles
详细说明
invokedynamic指令
Java 8 Lambda表达式使用invokedynamic指令实现，这是Java 7引入的动态调用机制：
0: invokedynamic #7, 0 // InvokeDynamic #0:apply:()Ljava/util/function/Function;
Lambda方法
编译器会为每个Lambda表达式生成一个私有静态方法（synthetic方法）：
private static java.lang.Integer lambda$lambdaExample$0(java.lang.String);
flags: ACC_PRIVATE, ACC_STATIC, ACC_SYNTHETIC
方法命名格式：lambda$方法名$序号
BootstrapMethods
BootstrapMethods属性存储引导方法信息，用于在运行时动态生成Lambda实现类：
BootstrapMethods:
0: #114 invokestatic java/lang/invoke/LambdaMetafactory.metafactory:(...)
Method arguments:
#100 (Ljava/lang/Object;)Ljava/lang/Object;
#101 invokestatic java/bytecode/LambdaExample.lambda$lambdaExample$0:(...)
#104 (Ljava/lang/String;)Ljava/lang/Integer;
LambdaMetafactory
LambdaMetafactory.metafactory是引导方法，在运行时：
1. 创建Lambda实现类
2. 将Lambda方法绑定到函数式接口
3. 返回CallSite对象
Lambda实现机制
- 编译时：编译器生成Lambda方法（如
lambda$lambdaExample$0） - 运行时：
invokedynamic调用引导方法 - 引导方法：使用
LambdaMetafactory动态生成实现类 - 调用：通过函数式接口调用Lambda方法
优势
- 延迟绑定：Lambda实现类在运行时生成，而不是编译时
- 性能优化：JVM可以优化Lambda调用
- 代码简洁：不需要为每个Lambda创建匿名内部类