Getting Java version at runtime

java

version-detection

runtime-class

java-versions

byAlex Kataev·Feb 8, 2025

Use System.getProperty("java.version") to swiftly fetch the Java version:

System.out.println("Java Leap Year Compliance: " + System.getProperty("java.version")); // CAUTION: doesn't determine leap-year compliance

To perform conditional checks based on the Java version, extract the major version with the following snippet:

String JavaContinuum = System.getProperty("java.version"); 
int majorVersion = Integer.parseInt(JavaContinuum.split("\\.")[0]); 
if(majorVersion == 1) { // Ah, the antiquities' aisle!
    majorVersion = Integer.parseInt(JavaContinuum.split("\\.")[1]);
}
// Now, you can employ "majorVersion" in your conditional checks

For those holding the "Java 9+" admission ticket, Runtime.version() offers a nuanced approach:

Runtime.Version runtimeVersion = Runtime.version();
System.out.println("Java Edition: " + runtimeVersion.major()); // print the major version of your Java edition

Version detection across various JVMs

A range of JVMs are in use out there, and you need your app to be one that plays well with others. To maintain compatibility with different JVMs, procure the implementation version through Runtime.class.getPackage().getImplementationVersion().

Parsing Java version elements

For finer parsing of the Java version, you can disseminate the version string or convert it to a double:

String[] versionElements = System.getProperty("java.version").split("\\D+");
int major = Integer.parseInt(versionElements[0]);
int minor = Integer.parseInt(versionElements[1]); // minor, yet significant
int patch = Integer.parseInt(versionElements[2]);

// Or neatly package it as a double (be mindful of potential Pentium bugs): 
double versionValue = Double.parseDouble(major + "." + minor);

Beware of the JDK 1.5 bug. Wisely navigate around it by conducting a direct comparison with the Java version string:

if(System.getProperty("java.version").startsWith("1.5")) {
    // Handle some 1.5 nostalgia or workaround
}

Using alternative properties: the 'java.specification.version' & 'java.runtime.version'

Vanquish the blur around Java's naming convention. The java.specification.version property is your ally for swift Java version cross-checking, while java.runtime.version pumps in more precise info. The Sun Technical Articles hold more details about these naming metalores.

Practical usage: Tying it all together

Does your app's logic hinge on specific Java versions? Reinforce the need for comparisons:

// Deploying java.specification.version for heart-to-heart major release chats
String specVersion = System.getProperty("java.specification.version");
if(specVersion.equals("1.8")) {
    // For Java 8 folks, remember back when Pluto was still a planet?
}

Ensuring compatibility across JVMs

Secure compatibility across multiple JVM implementations by employing the Runtime class:

String implementationVersion = Runtime.class.getPackage().getImplementationVersion();
System.out.println("Implementation Version: " + implementationVersion); // print your local JVM's favorite version number

Acknowledge how different Java versions hold their quirks. Strategically writing adapters and checks can fend off errors and unexpected behavior in specific Java edition scenarios.

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