Well other than most parts are stolen from other sites:

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Java’s Magic : The Byte code

The key that allows java to solve both the security and the portability problems is that the output of a java compiler is not executable code. Rather, it is a byte code.

Byte code is highly optimized set of instructions designed to be executed by the java run-time system, which is called java virtual machine (JVM) . That is in the standard form, the JVM is the interpreter for bytecode.
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Java’s Magic: The Bytecode

The secret behind the security and portability of Java is that the output of a Java compiler is not executable code. Rather, it is bytecode

Bytecode is a highly optimized set of instructions designed to be executed by the Java run-time system, which is called the Java
And thanks for the scan DjM.. much appreciated...

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