公司的开发环境比较老，寻找一些jar包的时候总是会纠结对应的编译版本，感觉很麻烦，所以写了一个工具类用于读取class或jar文件的编译版本，供大家参考。
package com.jinggujin.util; import java.io.DataInputStream; import java.io.File; import java.io.FileInputStream; import java.io.InputStream; import java.util.Enumeration; import java.util.jar.JarEntry; import java.util.jar.JarFile; /** * Java 版本工具 * * @author jianggujin * */ public class JavaVersionUtils { private static final int JAVA_CLASS_MAGIC = 0xCAFEBABE; public final static int JDK_1_2 = 46; public final static int JDK_1_3 = 47; public final static int JDK_1_4 = 48; public final static int JDK_5 = 49; public final static int JDK_6 = 50; public final static int JDK_7 = 51; public final static int JDK_8 = 52; /** * 获得当前环境JDK版本 * * @return */ public static int getJDKVersion() { String version = System.getProperty("java.version"); if (version != null && version.matches("1\\.\\d.*")) { int v = Integer.parseInt(version.charAt(2) + ""); if (v >= 2) { return 44 + v; } } return -1; } /** * 获得class或jar编译版本 * * @param file * @return * @throws Exception */ public static int getCompileVersion(File file) throws Exception { if (file == null || !file.isFile() || !file.getName().matches(".*\\.((jar)|(class))")) { throw new IllegalArgumentException("the file must be a jar or class."); } int version = -1; if (file.getName().endsWith("jar")) { JarFile jarFile = new JarFile(file); Enumeration<JarEntry> enumeration = jarFile.entries(); while (enumeration.hasMoreElements()) { JarEntry entry = enumeration.nextElement(); if (entry.getName().endsWith(".class")) { InputStream in = jarFile.getInputStream(entry); version = getVersion(in); in.close(); break; } } jarFile.close(); } else { InputStream in = new FileInputStream(file); version = getVersion(in); in.close(); } return version; } private static int getVersion(InputStream in) throws Exception { DataInputStream dis = new DataInputStream(in); //前面4个字节CA FE BA BE 是固定的，之后2个字节是次版本号，次版本号后面的2个字节是jdk的版本号 int magic = dis.readInt(); if (magic == JAVA_CLASS_MAGIC) { // int minorVersion = dis.readUnsignedShort(); int majorVersion = dis.readUnsignedShort(); // Java 1.2 >> 46 // Java 1.3 >> 47 // Java 1.4 >> 48 // Java 5 >> 49 // Java 6 >> 50 // Java 7 >> 51 // Java 8 >> 52 return majorVersion; } return -1; } }