CISC 124 Lecture Notes - Lecture 3: Java Virtual Machine, Java Bytecode, High-Level Programming Language
6 Mar 2017
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Interpreter/executer: platform dependent, advantages, fast, protected, easy to exchange, disadvantages, needs jvm installed. Java program structure: every java program is an object, class, modifier (public, private) keyword (class) name (world) , method heading, modifiers (public, static) return-type (void) name (main) arguments. Java translation: source code = classname. java, compiled by java compiler, low-level bytecode = classname. class, executed by jvm. Lecture 4: variables and assignments: semicolons everywhere, brackets instead of indentation, still indent for program style and reader understanding, declare all variables with type, ex. Int x = 0, y =1: static typing, type of variable known at compiler time, not runtime, compiler allocates appropriate memory space based on, type checking at compile time, data types in java data type, primitive, boolean, character. Integer: byte, short, int, long, floating-point numbers, float, double, non-primitive, string, array, integers. Int i = 2. 9 error: double d = 2 no compiler error, explicit type conversion. Int i = (int) 2. 9: opposite direction, returns 2, returns 3.
