Java example source code file (javap.1)

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The javap.1 Java example source code

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.\"
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.\" This code is free software; you can redistribute it and/or modify it
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.\" published by the Free Software Foundation.
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.\" version 2 for more details (a copy is included in the LICENSE file that
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.\" Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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.\" or visit www.oracle.com if you need additional information or have any
.\" questions.
.\"
.\"     Arch: generic
.\"     Software: JDK 8
.\"     Date: 21 November 2013
.\"     SectDesc: Basic Tools
.\"     Title: javap.1
.\"
.if n .pl 99999
.TH javap 1 "21 November 2013" "JDK 8" "Basic Tools"
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.SH NAME    
javap \- Disassembles one or more class files\&.
.SH SYNOPSIS    
.sp     
.nf     

\fBjavap\fR [\fIoptions\fR] \fIclassfile\fR\&.\&.\&.
.fi     
.sp     
.TP     
\fIoptions\fR
The command-line options\&. See Options\&.
.TP     
\fIclassfile\fR
One or more classes separated by spaces to be processed for annotations such as DocFooter\&.class\&. You can specify a class that can be found in the class path, by its file name or with a URL such as \f3file:///home/user/myproject/src/DocFooter\&.class\fR\&.
.SH DESCRIPTION    
The \f3javap\fR command disassembles one or more class files\&. The output depends on the options used\&. When no options are used, then the \f3javap\fR command prints the package, protected and public fields, and methods of the classes passed to it\&. The \f3javap\fR command prints its output to \f3stdout\fR\&.
.SH OPTIONS    
.TP
-help, --help, -?
.br
Prints a help message for the \f3javap\fR command\&.
.TP
-version
.br
Prints release information\&.
.TP
-l
.br
Prints line and local variable tables\&.
.TP
-public
.br
Shows only public classes and members\&.
.TP
-protected
.br
Shows only protected and public classes and members\&.
.TP
-private, -p
.br
Shows all classes and members\&.
.TP
-J\fIoption\fR
.br
Passes the specified option to the JVM\&. For example:
.sp     
.nf     
\f3javap \-J\-version\fP
.fi     
.nf     
\f3javap \-J\-Djava\&.security\&.manager \-J\-Djava\&.security\&.policy=MyPolicy MyClassName\fP
.fi     
.nf     
\f3\fP
.fi     
.sp     


For more information about JVM options, see the \f3java(1)\fR command documentation\&.
.TP
-s
.br
Prints internal type signatures\&.
.TP
-sysinfo
.br
Shows system information (path, size, date, MD5 hash) of the class being processed\&.
.TP
-constants
.br
Shows \f3static final\fR constants\&.
.TP
-c
.br
Prints disassembled code, for example, the instructions that comprise the Java bytecodes, for each of the methods in the class\&.
.TP
-verbose
.br
Prints stack size, number of locals and arguments for methods\&.
.TP
-classpath \fIpath\fR
.br
Specifies the path the \f3javap\fR command uses to look up classes\&. Overrides the default or the \f3CLASSPATH\fR environment variable when it is set\&.
.TP
-bootclasspath \fIpath\fR
.br
Specifies the path from which to load bootstrap classes\&. By default, the bootstrap classes are the classes that implement the core Java platform located in \f3jre/lib/rt\&.jar\fR and several other JAR files\&.
.TP
-extdir \fIdirs\fR
.br
Overrides the location at which installed extensions are searched for\&. The default location for extensions is the value of \f3java\&.ext\&.dirs\fR\&.
.SH EXAMPLE    
Compile the following \f3DocFooter\fR class:
.sp     
.nf     
\f3import java\&.awt\&.*;\fP
.fi     
.nf     
\f3import java\&.applet\&.*;\fP
.fi     
.nf     
\f3\fP
.fi     
.nf     
\f3public class DocFooter extends Applet {\fP
.fi     
.nf     
\f3        String date;\fP
.fi     
.nf     
\f3        String email;\fP
.fi     
.nf     
\f3\fP
.fi     
.nf     
\f3        public void init() {\fP
.fi     
.nf     
\f3                resize(500,100);\fP
.fi     
.nf     
\f3                date = getParameter("LAST_UPDATED");\fP
.fi     
.nf     
\f3                email = getParameter("EMAIL");\fP
.fi     
.nf     
\f3        }\fP
.fi     
.nf     
\f3\fP
.fi     
.nf     
\f3        public void paint(Graphics g) {\fP
.fi     
.nf     
\f3                g\&.drawString(date + " by ",100, 15);\fP
.fi     
.nf     
\f3                g\&.drawString(email,290,15);\fP
.fi     
.nf     
\f3        }\fP
.fi     
.nf     
\f3}\fP
.fi     
.nf     
\f3\fP
.fi     
.sp     
The output from the \f3javap DocFooter\&.class\fR command yields the following:
.sp     
.nf     
\f3Compiled from "DocFooter\&.java"\fP
.fi     
.nf     
\f3public class DocFooter extends java\&.applet\&.Applet {\fP
.fi     
.nf     
\f3  java\&.lang\&.String date;\fP
.fi     
.nf     
\f3  java\&.lang\&.String email;\fP
.fi     
.nf     
\f3  public DocFooter();\fP
.fi     
.nf     
\f3  public void init();\fP
.fi     
.nf     
\f3  public void paint(java\&.awt\&.Graphics);\fP
.fi     
.nf     
\f3}\fP
.fi     
.nf     
\f3\fP
.fi     
.sp     
The output from \f3javap -c DocFooter\&.class\fR command yields the following:
.sp     
.nf     
\f3Compiled from "DocFooter\&.java"\fP
.fi     
.nf     
\f3public class DocFooter extends java\&.applet\&.Applet {\fP
.fi     
.nf     
\f3  java\&.lang\&.String date;\fP
.fi     
.nf     
\f3  java\&.lang\&.String email;\fP
.fi     
.nf     
\f3\fP
.fi     
.nf     
\f3  public DocFooter();\fP
.fi     
.nf     
\f3    Code:\fP
.fi     
.nf     
\f3       0: aload_0       \fP
.fi     
.nf     
\f3       1: invokespecial #1                  // Method\fP
.fi     
.nf     
\f3java/applet/Applet\&."<init>":()V\fP
.fi     
.nf     
\f3       4: return        \fP
.fi     
.nf     
\f3\fP
.fi     
.nf     
\f3  public void init();\fP
.fi     
.nf     
\f3    Code:\fP
.fi     
.nf     
\f3       0: aload_0       \fP
.fi     
.nf     
\f3       1: sipush        500\fP
.fi     
.nf     
\f3       4: bipush        100\fP
.fi     
.nf     
\f3       6: invokevirtual #2                  // Method resize:(II)V\fP
.fi     
.nf     
\f3       9: aload_0       \fP
.fi     
.nf     
\f3      10: aload_0       \fP
.fi     
.nf     
\f3      11: ldc           #3                  // String LAST_UPDATED\fP
.fi     
.nf     
\f3      13: invokevirtual #4                  // Method\fP
.fi     
.nf     
\f3 getParameter:(Ljava/lang/String;)Ljava/lang/String;\fP
.fi     
.nf     
\f3      16: putfield      #5                  // Field date:Ljava/lang/String;\fP
.fi     
.nf     
\f3      19: aload_0       \fP
.fi     
.nf     
\f3      20: aload_0       \fP
.fi     
.nf     
\f3      21: ldc           #6                  // String EMAIL\fP
.fi     
.nf     
\f3      23: invokevirtual #4                  // Method\fP
.fi     
.nf     
\f3 getParameter:(Ljava/lang/String;)Ljava/lang/String;\fP
.fi     
.nf     
\f3      26: putfield      #7                  // Field email:Ljava/lang/String;\fP
.fi     
.nf     
\f3      29: return        \fP
.fi     
.nf     
\f3\fP
.fi     
.nf     
\f3  public void paint(java\&.awt\&.Graphics);\fP
.fi     
.nf     
\f3    Code:\fP
.fi     
.nf     
\f3       0: aload_1       \fP
.fi     
.nf     
\f3       1: new           #8                  // class java/lang/StringBuilder\fP
.fi     
.nf     
\f3       4: dup           \fP
.fi     
.nf     
\f3       5: invokespecial #9                  // Method\fP
.fi     
.nf     
\f3 java/lang/StringBuilder\&."<init>":()V\fP
.fi     
.nf     
\f3       8: aload_0       \fP
.fi     
.nf     
\f3       9: getfield      #5                  // Field date:Ljava/lang/String;\fP
.fi     
.nf     
\f3      12: invokevirtual #10                 // Method\fP
.fi     
.nf     
\f3 java/lang/StringBuilder\&.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;\fP
.fi     
.nf     
\f3      15: ldc           #11                 // String  by \fP
.fi     
.nf     
\f3      17: invokevirtual #10                 // Method\fP
.fi     
.nf     
\f3 java/lang/StringBuilder\&.append:(Ljava/lang/String;)Ljava/lang/StringBuilder;\fP
.fi     
.nf     
\f3      20: invokevirtual #12                 // Method\fP
.fi     
.nf     
\f3 java/lang/StringBuilder\&.toString:()Ljava/lang/String;\fP
.fi     
.nf     
\f3      23: bipush        100\fP
.fi     
.nf     
\f3      25: bipush        15\fP
.fi     
.nf     
\f3      27: invokevirtual #13                 // Method\fP
.fi     
.nf     
\f3 java/awt/Graphics\&.drawString:(Ljava/lang/String;II)V\fP
.fi     
.nf     
\f3      30: aload_1       \fP
.fi     
.nf     
\f3      31: aload_0       \fP
.fi     
.nf     
\f3      32: getfield      #7                  // Field email:Ljava/lang/String;\fP
.fi     
.nf     
\f3      35: sipush        290\fP
.fi     
.nf     
\f3      38: bipush        15\fP
.fi     
.nf     
\f3      40: invokevirtual #13                 // Method\fP
.fi     
.nf     
\f3java/awt/Graphics\&.drawString:(Ljava/lang/String;II)V\fP
.fi     
.nf     
\f3      43: return        \fP
.fi     
.nf     
\f3}\fP
.fi     
.nf     
\f3\fP
.fi     
.sp     
.SH SEE\ ALSO    
.TP 0.2i    
\(bu
javac(1)
.TP 0.2i    
\(bu
java(1)
.TP 0.2i    
\(bu
jdb(1)
.TP 0.2i    
\(bu
javah(1)
.TP 0.2i    
\(bu
javadoc(1)
.RE
.br
'pl 8.5i
'bp