long and double types, which are 64 bits, take up two consecutive local variables : 2.6.1 (which need not be 64-bit aligned in the local variables array) or one value in the operand stack (but are counted as two units in the depth of the stack). : 4.7.3 Each can be independently sized from 0 to 65535 values, where each value is 32 bits. The maximum size of the operand stack and local variable array, computed by the compiler, is part of the attributes of each method. : 2.6 The operand stack is used for operands to computations and for receiving the return value of a called method, while local variables serve the same purpose as registers and are also used to pass method arguments. Each frame for a method call has an "operand stack" and an array of "local variables". The JVM is both a stack machine and a register machine. However, as suggested in the IBM developerWorks journal, "Understanding bytecode and what bytecode is likely to be generated by a Java compiler helps the Java programmer in the same way that knowledge of assembly helps the C or C++ programmer." Instruction set architecture In computing, Java bytecode is the bytecode-structured instruction set of the Java virtual machine (JVM), a virtual machine that enables a computer to run programs written in the Java programming language and several other programming languages, see List of JVM languages.Ī Java programmer does not need to be aware of or understand Java bytecode at all. Please consider expanding the lead to provide an accessible overview of all important aspects of the article. This article's lead section may be too short to adequately summarize the key points.
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