java class文件怎么看?
查看class文件方法有很多种,这里推荐使用JDK自带的javap工具。
首先建立如下源码:
public class HelloWorld{ public static void main(String[] args){ System.out.println(Hello World!); } }
使用javac编译器把源文件编译好,再接着使用javap工具查看class文件,命令如下
javap -verbose HelloWorld
这是DOS窗口的运行结果复制出来如下图:
F:\>javac HelloWorld.java F:\>javap -verbose HelloWorld Classfile /F:/HelloWorld.class Last modified 2017-12-24; size 426 bytes MD5 checksum 4efac412ef483c8a3fe7489c87d15c8c Compiled from HelloWorld.java public class HelloWorld minor version: 0 major version: 52 flags: ACC_PUBLIC, ACC_SUPER Constant pool: #1 = Methodref #6.#15 // java/lang/Object.<init>:()V #2 = Fieldref #16.#17 // java/lang/System.out:Ljava/io/Print Stream; #3 = String #18 // Hello World! #4 = Methodref #19.#20 // java/io/PrintStream.println:(Ljava/ lang/String;)V #5 = Class #21 // HelloWorld #6 = Class #22 // java/lang/Object #7 = Utf8 <init> #8 = Utf8 ()V #9 = Utf8 Code #10 = Utf8 LineNumberTable #11 = Utf8 main #12 = Utf8 ([Ljava/lang/String;)V #13 = Utf8 SourceFile #14 = Utf8 HelloWorld.java #15 = NameAndType #7:#8 // <init>:()V #16 = Class #23 // java/lang/System #17 = NameAndType #24:#25 // out:Ljava/io/PrintStream; #18 = Utf8 Hello World! #19 = Class #26 // java/io/PrintStream #20 = NameAndType #27:#28 // println:(Ljava/lang/String;)V #21 = Utf8 HelloWorld #22 = Utf8 java/lang/Object #23 = Utf8 java/lang/System #24 = Utf8 out #25 = Utf8 Ljava/io/PrintStream; #26 = Utf8 java/io/PrintStream #27 = Utf8 println #28 = Utf8 (Ljava/lang/String;)V { public HelloWorld(); 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 1: 0 public static void main(java.lang.String[]); descriptor: ([Ljava/lang/String;)V flags: ACC_PUBLIC, ACC_STATIC Code: stack=2, locals=1, args_size=1 0: getstatic #2 // Field java/lang/System.out:Ljav a/io/PrintStream; 3: ldc #3 // String Hello World! 5: invokevirtual #4 // Method java/io/PrintStream.prin tln:(Ljava/lang/String;)V 8: return LineNumberTable: line 3: 0 line 4: 8 } SourceFile: HelloWorld.java F:\>
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