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‎JavaInfo‎

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#!/usr/bin/perl
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################################################################################
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# JavaInfo - Java Class File Version Analyzer
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#
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# This utility extracts Java version information from compiled class files by
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# reading their bytecode headers. It recursively processes files and directories
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# to identify Java class files and report their compilation version.
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#
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# The script reads the first 8 bytes of each file, checks for the Java class
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# file magic number (0xCAFEBABE), and extracts the major/minor version numbers
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# which indicate the Java version used to compile the class.
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#
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# Usage: JavaInfo <file or directory> [<file or directory> ...]
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#
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# Examples:
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# JavaInfo MyClass.class
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# JavaInfo /path/to/project/bin
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# JavaInfo target/classes lib/*.jar
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#
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# Author: Thomas
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# License: See LICENSE file
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################################################################################
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use strict;
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use warnings;
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use File::Spec::Functions;
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#
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# Main entry point - processes all command-line arguments
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#
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# Parameters:
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# @_ - List of file or directory paths to process
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#
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sub main {
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foreach my $node (@_) {
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process_node($node);
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}
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}
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#
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# Process a filesystem node (file or directory)
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#
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# Determines whether the given path is a file or directory and dispatches
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# to the appropriate handler function.
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#
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# Parameters:
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# $node - Path to the filesystem node to process
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#
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sub process_node {
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my $node = shift();
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if (-f $node) {
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}
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}
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#
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# Recursively process all files in a directory
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#
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# Reads all entries in the directory (excluding . and ..) and recursively
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# processes each one by calling process_node.
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#
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# Parameters:
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# $dir - Path to the directory to process
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#
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# Dies on error:
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# - If the directory cannot be opened
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# - If the directory contents cannot be read
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#
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sub process_dir {
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my $dir = shift();
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if (opendir(my $DIR, $dir)) {
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}
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}
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#
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# Process a single file and extract Java version information
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#
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# Reads the first 8 bytes of a file to check if it's a valid Java class file
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# (identified by the magic number 0xCAFEBABE) and extracts version information
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# from the bytecode header.
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#
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# Java class file format (first 8 bytes):
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# Bytes 0-3: Magic number (0xCAFEBABE)
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# Bytes 4-5: Minor version
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# Bytes 6-7: Major version
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#
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# Version mapping:
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# Major 45 (minor <=3): Java 1.0.2
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# Major 45 (minor >3): Java 1.1.8
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# Major 46: Java 1.2.2
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# Major 47: Java 1.3.1
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# Major 48: Java 1.4.2
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# Major 49+: Java (major - 44) [e.g., 52 = Java 8, 61 = Java 17]
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#
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# Parameters:
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# $file - Path to the file to process
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#
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# Dies on error:
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# - If the file cannot be opened
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# - If the file cannot be read
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# - If the file is not a valid Java class file
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#
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sub process_file {
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my $file = shift();
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if (open(my $FILE, '<', $file)) {
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binmode($FILE);
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my $buffer;
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if (read(FILE, $buffer, 8)) {
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# Unpack the first 8 bytes as two 32-bit unsigned integers (big-endian)
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my @fields = unpack('NN', $buffer);
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# Check for Java class file magic number (0xCAFEBABE)
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if ($fields[0] == 0xCAFEBABE) {
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# Extract minor and major version numbers from the second 32-bit value
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my $minor = ($fields[1] & 0xFF00) >> 16; ## no critic [Use of bitwise operator]: indeed
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my $major = $fields[1] & 0x00FF; ## no critic [Use of bitwise operator]: indeed
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my $version = '';
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# Map major/minor version to Java release version
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if ($major == 45) {
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if ($minor <= 3) {
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$version = '1.0.2';
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} elsif ($major == 48) {
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$version = '1.4.2';
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} elsif ($major >= 49) {
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# Java 5 and later: version = major - 44
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$version = ($major - 44);
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}
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print "$file: Java " . $version . " [" . $minor . "/" . $major . "]\n";

‎README.md‎

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# JavaInfo
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Perl utility to extract the Java version info from a class file's bytecode.
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A Perl utility to extract Java version information from compiled Java class files by analyzing their bytecode headers.
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[![PerlCritic](https://github.com/thomasleplus/JavaInfo/workflows/PerlCritic/badge.svg)](https://github.com/thomasleplus/JavaInfo/actions?query=workflow:"PerlCritic")
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## Description
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JavaInfo reads Java `.class` files and identifies the Java version used to compile them. It works by examining the bytecode header of each class file, specifically the magic number (`0xCAFEBABE`) and the major/minor version numbers that indicate the Java compiler version.
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The tool can process individual files or recursively scan entire directories, making it useful for:
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- Auditing Java dependencies and libraries
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- Verifying compilation targets in build artifacts
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- Identifying version mismatches in projects
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- Understanding compatibility requirements
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## Requirements
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- Perl 5.x or later
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- Standard Perl modules (included by default):
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- `File::Spec::Functions`
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## Installation
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1. Clone or download this repository
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2. Make the script executable:
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```bash
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chmod +x JavaInfo
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```
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3. Optionally, add it to your PATH:
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```bash
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sudo cp JavaInfo /usr/local/bin/
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```
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## Usage
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```bash
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./JavaInfo <file or directory> [<file or directory> ...]
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```
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### Examples
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**Analyze a single class file:**
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```bash
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./JavaInfo MyClass.class
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```
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**Scan a directory recursively:**
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```bash
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./JavaInfo /path/to/project/target/classes
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```
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**Process multiple paths:**
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```bash
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./JavaInfo src/main/java build/classes lib/*.jar
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```
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### Example Output
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```
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MyClass.class: Java 11 [0/55]
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Utils.class: Java 8 [0/52]
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LegacyCode.class: Java 1.4.2 [0/48]
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```
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The output format is:
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```
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<filename>: Java <version> [<minor>/<major>]
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```
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Where:
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- `<filename>` is the path to the class file
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- `<version>` is the Java version (e.g., 8, 11, 17, or 1.4.2 for older versions)
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- `<minor>/<major>` are the bytecode version numbers
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## Java Version Mapping
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The tool uses the following mapping between bytecode major versions and Java releases:
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| Major Version | Minor Version | Java Version |
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|--------------|---------------|--------------|
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| 45 | 0-3 | 1.0.2 |
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| 45 | 4+ | 1.1.8 |
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| 46 | - | 1.2.2 |
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| 47 | - | 1.3.1 |
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| 48 | - | 1.4.2 |
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| 49 | - | 5 |
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| 50 | - | 6 |
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| 51 | - | 7 |
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| 52 | - | 8 |
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| 53 | - | 9 |
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| 54 | - | 10 |
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| 55 | - | 11 |
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| 56 | - | 12 |
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| 57 | - | 13 |
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| 58 | - | 14 |
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| 59 | - | 15 |
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| 60 | - | 16 |
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| 61 | - | 17 |
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| 62 | - | 18 |
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| 63 | - | 19 |
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| 64 | - | 20 |
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| 65 | - | 21 |
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For Java 5 and later, the formula is: **Java Version = Major Version - 44**
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## Error Handling
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The script will display error messages and exit if:
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- A file cannot be opened or read
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- A directory cannot be accessed
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- A file is not a valid Java class file (missing the `0xCAFEBABE` magic number)
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## Contributing
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Contributions are welcome! Please see [CONTRIBUTING.md](CONTRIBUTING.md) for guidelines.
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## License
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See [LICENSE](LICENSE) file for details.
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## Security
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For security concerns, please see [SECURITY.md](SECURITY.md).
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## Code of Conduct
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This project adheres to a code of conduct. See [CODE_OF_CONDUCT.md](CODE_OF_CONDUCT.md) for details.

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