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JDK 1.5 introduced some changes in some of the core classes. In particular java.lang.StringBuffer was given a superclass of java.lang.AbstractStringBuilder. Code compiled with the javasoft 1.5 compiler does run in earlier versions of the VM. If you build the classes using the eclipse compiler, there seems to be a built in hook to the superclass. Thus the classes won't run in earlier versions of the vm. A ClassNotFoundException for java.lang.AbstractStringBuilder is thrown.
Please provide steps to reproduce. Also to be a fair comparison, you should try to achieve the result with javac 1.4, as the Eclipse compiler you are using is a 1.4 compiler (moving to 1.5, but not yet there).
Install the latest 1.5 beta Set Eclipse to use the 1.5 JRE in the installed JREs ALso set it to use the 1.4.2_02 jre (which 1.4 version shouldn't matter) Create the following file in Eclipse public class StringBufferTest { public static void main(String[] args) { StringBuffer a = new StringBuffer(); a.append("This is a test"); System.out.println(a.toString()); System.exit(0); } } Build and run it. Now switch the runtime VM to 1.4 in the run... dialog. Re run without rebuilding It fails. Below is the output of my sessions outside eclipse from this point on. As you can see before rebuilding it fails. After rebuilding it works. Note that I did have to use the -target 1.4 switch on the compiler but Eclipse doesn't have such a switch to my knowledge. C:\eclipse\workspace\test>dir Volume in drive C is WXP Volume Serial Number is 08E8-C1C4 Directory of C:\eclipse\workspace\test 02/24/2004 04:05 PM <DIR> . 02/24/2004 04:05 PM <DIR> .. 02/24/2004 03:57 PM 226 .classpath 02/24/2004 03:57 PM 380 .project 02/24/2004 04:05 PM 804 StringBufferTest.class 02/24/2004 03:58 PM 552 StringBufferTest.java 4 File(s) 1,962 bytes 2 Dir(s) 1,767,754,752 bytes free C:\eclipse\workspace\test>java -classpath . StringBufferTest This is a test C:\eclipse\workspace\test>java -version java version "1.5.0-beta" Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0-beta-b32c) Java HotSpot(TM) Client VM (build 1.5.0-beta-b32c, mixed mode) C:\eclipse\workspace\test>"c:\Program Files\java\j2re1.4.2_02\bin\java" - classpa th . StringBufferTest Exception in thread "main" java.lang.NoSuchMethodError: java.lang.StringBuffer.a ppend(Ljava/lang/String;)Ljava/lang/AbstractStringBuilder; at StringBufferTest.main(StringBufferTest.java:19) C:\eclipse\workspace\test>c:\jdk1.5.0\bin\javac -classpath . StringBufferTest.ja va C:\eclipse\workspace\test>java -classpath . StringBufferTest This is a test C:\eclipse\workspace\test>"c:\Program Files\java\j2re1.4.2_02\bin\java" - classpa th . StringBufferTest Exception in thread "main" java.lang.UnsupportedClassVersionError: StringBufferT est (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) C:\eclipse\workspace\test>c:\jdk1.5.0\bin\javac -target 1.4 -classpath . StringB ufferTest.java C:\eclipse\workspace\test>"c:\Program Files\java\j2re1.4.2_02\bin\java" - classpa th . StringBufferTest This is a test C:\eclipse\workspace\test>java -classpath . StringBufferTest This is a test C:\eclipse\workspace\test>c:\jdk1.4.2_02\bin\javac -classpath . StringBufferTest .java The system cannot find the path specified. C:\eclipse\workspace\test>c:\j2sdk1.4.2_02\bin\javac -classpath . StringBufferTe st.java C:\eclipse\workspace\test>java -classpath . StringBufferTest This is a test C:\eclipse\workspace\test>"c:\Program Files\java\j2re1.4.2_02\bin\java" - classpa th . StringBufferTest This is a test
Note that in your script, it shows that when using javac 1.4 you did compile against 1.4 libraries (by default).
Yes, but when I compiled against 1.5, I ran against 1.4 libraries with no problem (using the javasoft compiler)
Understood, but your point was to use a 1.4 compiler to compile against JDK1.5 and then run against 1.4. Javac doesn't support it, as it refuses to compile against more recent libraries. We may still have an obvious issue leading us to misbehave, will investigate.
I recompiled the classes, first with Eclipse and then with jdk 1.5. I dumped out each class and Eclipse has compiled in the return type differently. C:\eclipse\workspace\test>c:\jdk1.5.0\bin\javap -classpath . -c StringBufferTest Compiled from "StringBufferTest.java" public class StringBufferTest extends java.lang.Object{ public StringBufferTest(); Code: 0: aload_0 1: invokespecial #9; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: new #17; //class java/lang/StringBuffer 3: dup 4: invokespecial #18; //Method java/lang/StringBuffer."<init>":()V 7: astore_1 8: aload_1 9: ldc #20; //String This is a test 11: invokevirtual #24; //Method java/lang/StringBuffer.append: (Ljava/lang/ String;)Ljava/lang/AbstractStringBuilder; 14: pop 15: getstatic #30; //Field java/lang/System.out:Ljava/io/PrintStream; 18: aload_1 19: invokevirtual #34; //Method java/lang/StringBuffer.toString:() Ljava/la ng/String; 22: invokevirtual #40; //Method java/io/PrintStream.println: (Ljava/lang/St ring;)V 25: iconst_0 26: invokestatic #44; //Method java/lang/System.exit:(I)V 29: return } C:\eclipse\workspace\test>c:\jdk1.5.0\bin\javac -target 1.4 -classpath . StringBufferTest.ja va C:\eclipse\workspace\test>c:\jdk1.5.0\bin\javap -classpath . -c StringBufferTest Compiled from "StringBufferTest.java" public class StringBufferTestextends java.lang.Object{ public StringBufferTest(); Code: 0: aload_0 1: invokespecial #1; //Method java/lang/Object."<init>":()V 4: return public static void main(java.lang.String[]); Code: 0: new #2; //class java/lang/StringBuffer 3: dup 4: invokespecial #3; //Method java/lang/StringBuffer."<init>":()V 7: astore_1 8: aload_1 9: ldc #4; //String This is a test 11: invokevirtual #5; //Method java/lang/StringBuffer.append: (Ljava/lang/S tring;)Ljava/lang/StringBuffer; 14: pop 15: getstatic #6; //Field java/lang/System.out:Ljava/io/PrintStream; 18: aload_1 19: invokevirtual #7; //Method java/lang/StringBuffer.toString:() Ljava/lan g/String; 22: invokevirtual #8; //Method java/io/PrintStream.println: (Ljava/lang/Str ing;)V 25: iconst_0 26: invokestatic #9; //Method java/lang/System.exit:(I)V 29: return }
Works fine now in latest, dup of bug 51353 *** This bug has been marked as a duplicate of 51353 ***
