The Java compiler and JDK have not been designed to work like this (using 1.3 JARs with the 1.5 compiler), so it's not certain that it's even possible, and your might get strange problems either at compile time or at runtime.
There's no official way to make this work and even if you manage to get it working, there's no guarantee that you'll get strange problems with the compiled classes.
If this is for a production code on a commercial, business project I would not take the risk to try something strange and unsupported like that.
Instead, I would first focus on finding ways to avoid the need to recompile the code so often. Is it really necessary to compile all those 14,000 source files so often? Is there a way to organize the sources in such a way that you only have to compile a small part if you make a change? Can you maybe setup a separate server which does the compiling at a moment when people don't have to wait for it (a nightly build, for example)?
(Ofcourse the compiler has "-source" and "-target" switches so that you can compile classes that are compatible with 1.3, but those unfortunately don't stop you from using Java 1.4+ API classes).
Cross Compilation with Respect to jdk7 step:1--create a java file example:EnhancedForLoop.java
step:2--compile the above EnhancedForLoop.java by using following command in windows cmd command prompt.here i am compiling jdk1.6 using jdk1.7.
before applying this command please make sure that your your should contains or points to the actual rt.jar file of intended jdkX.X(1.1 or 1.2 or 1.3 or 1.4 or 1.5 or 1.6 etc)of and folder name should not contains spaces for example like in windows default place to be installation of softwares is here program files folder name have spaces.
means the file contained source like enhanced for loop feature introduced in jdk1.5v like wise there may be possibility of your .java file may have some code specific to that jdk versions.
note that it is always as same as .
describes the your converted type means cross compilation type. here i am using jdk7 , hence to make jdk1.6 compiler available in jdk1.7 i used this option.