Why java is suitable for internet?

Java is suitable for internet because of two main reasons.

1. It is system independent and hence its programs can run on any type of computer available on  internet.
2. It eliminates a lot of security problems for data on internet.

What is the difference between an executable(.exe) file and .CLASS file?

The .exe file contains machine language instructions for the microprocessor and is system dependent. .CLASS file contains byte code instructions for the JVM and is system idependent.