IDE与classpath的区别

[hwsjtu]

为什么我在IDE中加入运行库 rt.jar就能正确运行得到输出，我用的IDE是intellij
而在CLASSPATH中加入运行库 rt.jar就不能正确运行呢？

得到的错误如下，该加的库都加了啊
Exception in thread "main" java.lang.UnsupportedClassVersionError: com/redcode
/j
axp/JAXPTransformer (Unsupported major.minor version 49.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at java.security.SecureClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.defineClass(Unknown Source)
at java.net.URLClassLoader.access$100(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClassInternal(Unknown Source)

[xtaotao]

"C:\j2sdk1.4.2_02\bin\javac.exe" -classpath "D:\java;C:\j2sdk1.4.2_02\jre\lib\rt.jar;C:\j2sdk1.4.2_02\lib\dt.jar;C:\j2sdk1.4.2_02\lib\tools.jar;C:\j2sdk1.4.2_02\jre\lib\ext\sunjce_provider.jar;C:\j2sdk1.4.2_02\jre\lib\ext\dnsns.jar;C:\j2sdk1.4.2_02\jre\lib\ext\ldapsec.jar;C:\j2sdk1.4.2_02\jre\lib\ext\localedata.jar;C:\Program Files\Apache Software Foundation\Tomcat 5.0\common\lib\servlet-api.jar" -d "D:\java" D:\java\test.java

这样写肯定不会出错,呵呵