JvmVersionUtil.java Source code

Introduction

Here is the source code for JvmVersionUtil.java

Source

//package com.javadocking.util;

/**
 * This class determines the version of the Java Virtual Machine.
 * 
 * @author Heidi Rakels.
 */
public class JvmVersionUtil {

    // Static fields.

    /** The integer for java 1.3 versions of the JVM. */
    public static final int VERSION_3_OR_LESS = 3;
    /** The integer for java 5 versions of the JVM. */
    public static final int VERSION_4_or_5 = 4;
    /** The integer for java 6 versions of the JVM. */
    public static final int VERSION_6_OR_MORE = 6;

    /** The float for java 4 versions of the JVM. */
    private static final float VERSION_4 = 1.4f;
    /** The integer for java 6 versions of the JVM. */
    private static final float VERSION_6 = 1.6f;

    // Public static methods.

    /**
     * Gets the version of the JVM.
     * 
     * @return The integer that corresponds with the version of the JVM. This
     *         can be VERSION_3_OR_LESS,VERSION_4_or_5, VERSION_6_OR_MORE.
     * @throws IllegalStateException
     *             If the system property <code>java.version</code> does not
     *             start with a x.x. x should be a number.
     */
    public static int getVersion() {

        // Get the system property java.vm.version.
        String jVersion = System.getProperty("java.version");

        // Get the version number.
        int pointPosition = jVersion.indexOf(".");
        if (pointPosition > 0) {
            if (jVersion.length() >= pointPosition + 2) {
                String version = jVersion.substring(0, pointPosition + 2);

                try {
                    float versionNumber = Float.parseFloat(version);
                    if (versionNumber < VERSION_4) {
                        return VERSION_3_OR_LESS;
                    }
                    if (versionNumber < VERSION_6) {
                        return VERSION_4_or_5;
                    } else {
                        return VERSION_6_OR_MORE;
                    }
                } catch (NumberFormatException exception) {
                    throw new IllegalStateException("Unknown java version [" + jVersion + "].");
                }
            }
        }

        throw new IllegalStateException("Unknown java version [" + jVersion + "].");

    }

    // Test.

    // public static void main(String[] args) {
    //
    // String version = System.getProperty("java.vm.version");
    // System.out.println("Version number: " + getVersion());
    // System.out.println("Version string: " + version);
    //
    // }

    // Private constructor.

    private JvmVersionUtil() {
    }
}