Jdk版本的判定（来源于Spring源码）

Jdk版本的判定（来自Spring源码）

/*
 * Copyright 2002-2004 the original author or authors.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core;

/**
 * Helper class used to find the current Java/JDK version.
 * Usually we want to find if we're in a 1.4 or higher JVM.
 * (Spring does not support 1.2 JVMs.)
 * 
 * @author Rod Johnson
 * @author Juergen Hoeller
 */
public class JdkVersion {

	public static final int JAVA_13 = 0;

	public static final int JAVA_14 = 1;

	public static final int JAVA_15 = 2;

	public static final int JAVA_16 = 3;

	public static final int JAVA_17 = 4;

	private static String javaVersion;

	private static int majorJavaVersion = JAVA_13;

	static {
		javaVersion = System.getProperty("java.version");
		// should look like "1.4.1_02"
		if (javaVersion.indexOf("1.4.") != -1) {
			majorJavaVersion = JAVA_14;
		} else if (javaVersion.indexOf("1.5.") != -1) {
			majorJavaVersion = JAVA_15;
		} else if (javaVersion.indexOf("1.6.") != -1) {
			majorJavaVersion = JAVA_16;
		} else if (javaVersion.indexOf("1.7.") != -1) {
			majorJavaVersion = JAVA_17;
		}
		// else leave as 1.3 default
	}

	/**
	 * Return the full Java version string, as returned by
	 * <code>System.getProperty("java.version")</code>.
	 */
	public static String getJavaVersion() {
		return javaVersion;
	}

	/**
	 * Get the major version code. This means we can do things like
	 * <code>if (getMajorJavaVersion() < JAVA_14)</code>.
	 * 
	 * @return a code comparable to the JAVA_XX codes in this class
	 * @see #JAVA_13
	 * @see #JAVA_14
	 * @see #JAVA_15
	 */
	public static int getMajorJavaVersion() {
		return majorJavaVersion;
	}

}