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Java in a Nutshell

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javap

Name

javap---The Java Class Disassembler

Availability

JDK 1.0 and later.

Synopsis

javap [ options ] classnames

Description

javap disassembles the class files specified by the class names on the command line and prints a human-readable version of those classes.

By default, javap prints declarations of the non-private members of each of the classes specified on the command line. The -l, -p, and -c options specify additional information to be printed, including a complete disassembly of the byte-codes in each of the specified classes. javap can also be used to run the class verifier on Java classes.

Options

-c

Print the Java Virtual Machine instructions for each of the methods in each of the specified classes. This option disassembles all methods, including private methods.

-classpath path

The path that javap uses to look up the classes named on the command line. This option overrides the default path and any path specified by the CLASSPATH environment variable. The path specified is an ordered list of directories and ZIP files, separated by colons on UNIX systems or semicolons on Windows systems.

To specify additional directories or ZIP files for javap to search without overriding the default system class path, use the CLASSPATH environment variable. See the java reference page for more information on specifying paths.

-h

Outputs the class in a form suitable for inclusion in a C header file.

-l

Prints line numbers and local variable tables in addition to the public fields of the class. Note that line numbers and local variable information is included for use with debuggers. Local variable information is available only if a class was compiled with the -g option to javac; line number information is available only if a class was compiled without the -O option.

-p

Prints private methods and variables of the specified class in addition to the public ones. Note that some compilers (though not javac) may allow this private field information to be "obfuscated" in such a way that private fields and method arguments no longer have meaningful names. This makes Java classes harder to disassemble or reverse engineer.

-s

Outputs the class member declarations using the internal Virtual Machine format.

-v

Verbose. Outputs additional information (in the form of Java comments) about each member of each specified class.

-verify

Causes javap to run the class verifier on the specified classes and display the results of verification.

-version

Causes javap to display its version number.

Environment

CLASSPATH

Specifies an ordered list (colon-separated on UNIX, semicolon-separated on Windows systems) of directories and ZIP files in which javap should look for class definitions. When a path is specified with this environment variable, javap always implicitly appends the location of the system classes to the end of the path. If this environment variable is not specified, the default path is the current directory and the system classes. This variable is overridden by the -classpath option.

See Also

java, javac


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