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"javap -v" - Verbose Mode
How to "javap" command use verbose mode to print additional information about the selected class.
✍: FYIcenter
You can use the "-v" or "-verbose" option of the "javap" command
to print additional information about the specified class bytecode.
1. Compile HelloWorldFrame.java used in the last tutorial into a bytecode file, HelloWorldFrame.class:
> javac HelloWorldFrame.java
2. Disassemble it using "javap" command with the "-v" option
> javap -v HelloWorldFrame.class Classfile HelloWorldFrame.class Last modified 2021; size 634 bytes SHA-256 checksum 9d6d07fecb3045d8b27d071419e34d02532ea1e1db9f27707d9e7ab474ff45a4 Compiled from "HelloWorldFrame.java" public class HelloWorldFrame extends javax.swing.JFrame minor version: 0 major version: 59 flags: (0x0021) ACC_PUBLIC, ACC_SUPER this_class: #10 // HelloWorldFrame super_class: #2 // javax/swing/JFrame interfaces: 0, fields: 1, methods: 2, attributes: 3 Constant pool: #1 = Methodref #2.#3 // javax/swing/JFrame."<init>":()V #2 = Class #4 // javax/swing/JFrame #3 = NameAndType #5:#6 // "<init>":()V #4 = Utf8 javax/swing/JFrame #5 = Utf8 <init> #6 = Utf8 ()V #7 = String #8 // Hello World! #8 = Utf8 Hello World! #9 = Fieldref #10.#11 // HelloWorldFrame.message:Ljava/lang/String; #10 = Class #12 // HelloWorldFrame #11 = NameAndType #13:#14 // message:Ljava/lang/String; #12 = Utf8 HelloWorldFrame #13 = Utf8 message #14 = Utf8 Ljava/lang/String; #15 = Class #16 // HelloWorldFrame$1 #16 = Utf8 HelloWorldFrame$1 #17 = Methodref #15.#18 // HelloWorldFrame$1."<init>":(LHelloWorldFrame;)V #18 = NameAndType #5:#19 // "<init>":(LHelloWorldFrame;)V #19 = Utf8 (LHelloWorldFrame;)V #20 = Methodref #10.#21 // HelloWorldFrame.setContentPane:(Ljava/awt/Container;)V #21 = NameAndType #22:#23 // setContentPane:(Ljava/awt/Container;)V #22 = Utf8 setContentPane #23 = Utf8 (Ljava/awt/Container;)V #24 = Methodref #10.#25 // HelloWorldFrame.setSize:(II)V #25 = NameAndType #26:#27 // setSize:(II)V #26 = Utf8 setSize #27 = Utf8 (II)V #28 = Methodref #10.#3 // HelloWorldFrame."<init>":()V #29 = Methodref #10.#30 // HelloWorldFrame.setVisible:(Z)V #30 = NameAndType #31:#32 // setVisible:(Z)V #31 = Utf8 setVisible #32 = Utf8 (Z)V #33 = Utf8 Code #34 = Utf8 LineNumberTable #35 = Utf8 main #36 = Utf8 ([Ljava/lang/String;)V #37 = Utf8 SourceFile #38 = Utf8 HelloWorldFrame.java #39 = Utf8 NestMembers #40 = Utf8 InnerClasses { java.lang.String message; descriptor: Ljava/lang/String; flags: (0x0000) public HelloWorldFrame(); descriptor: ()V flags: (0x0001) ACC_PUBLIC Code: stack=4, locals=1, args_size=1 0: aload_0 1: invokespecial #1 // Method javax/swing/JFrame."<init>":()V 4: aload_0 5: ldc #7 // String Hello World! 7: putfield #9 // Field message:Ljava/lang/String; 10: aload_0 11: new #15 // class HelloWorldFrame$1 14: dup 15: aload_0 16: invokespecial #17 // Method HelloWorldFrame$1."<init>":(LHelloWorldFrame;)V 19: invokevirtual #20 // Method setContentPane:(Ljava/awt/Container;)V 22: aload_0 23: bipush 100 25: bipush 100 27: invokevirtual #24 // Method setSize:(II)V 30: return LineNumberTable: line 8: 0 line 6: 4 line 9: 10 line 15: 22 line 16: 30 public static void main(java.lang.String[]); descriptor: ([Ljava/lang/String;)V flags: (0x0009) ACC_PUBLIC, ACC_STATIC Code: stack=2, locals=2, args_size=1 0: new #10 // class HelloWorldFrame 3: dup 4: invokespecial #28 // Method "<init>":()V 7: astore_1 8: aload_1 9: iconst_1 10: invokevirtual #29 // Method setVisible:(Z)V 13: return LineNumberTable: line 18: 0 line 19: 8 line 20: 13 } SourceFile: "HelloWorldFrame.java" NestMembers: HelloWorldFrame$1 InnerClasses: #15; // class HelloWorldFrame$1
⇒ "javap -v" - Major Version Code
2021-09-09, 937🔥, 0💬
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