VersionUtil.java

package org.slf4j.impl;

import java.lang.reflect.Method;

import org.slf4j.helpers.Util;

public class VersionUtil {
	static final int MINIMAL_VERSION = 5;

	static public int getJavaMajorVersion() {
		String javaVersionString = Util.safeGetSystemProperty("java.version");
		return getJavaMajorVersion(javaVersionString);
	}

	static int getJavaMajorVersion(String versionString) {
		if (versionString == null)
			return MINIMAL_VERSION;
		if (versionString.startsWith("1.")) {
			return versionString.charAt(2) - '0';
		} else {
			// we running under Java 9 or later
			try {
				Method versionMethod = Runtime.class.getMethod("version");
				Object versionObj = versionMethod.invoke(null);
				Method majorMethod = versionObj.getClass().getMethod("major");
				Integer resultInteger = (Integer) majorMethod.invoke(versionObj);
				return resultInteger.intValue();
			} catch (Exception e) {
				return MINIMAL_VERSION;
			}
		}
	}
}