Mega Code Archive
This class determines the version of the Java Virtual Machine
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//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() {
}
}
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