To implement the Java Virtual Machine(JVM) correctly, you need only be able to read the class file format and correctly perform the operations specified therein. Implementation details that are not part of the Java Virtual Machine's specification would unnecessarily constrain the creativity of implementors.
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JVM Architecture shows the actual picture of JVM Which helps you to understand the internal flow for JVM.
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It is possible to increase heap size allocated by the Java Virtual Machine (JVM) by using command line options. Example for changing the Heap size is given here.
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