Code Size/Cheat sheet

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Code Size Cheat sheet

Do and Don't Do Don't class Robot extends AdvancedRobot { static double varname; public void run() { LinkedList list; try{ someFunction (list.getFirst()); } catch(Exception ex){} int i = 1; if (j > 2) { i = -1; } } public void onScannedRobot (ScannedRobotEvent e) double a; double t = getEnergy() * (a = e.getBearing()); } } class Robot extends AdvancedRobot { double varname = 0; public void run() { LinkedList list; if(list.size() != 0){ someFunction (list.getFirst()); } int i; if (j > 2) { i = -1; } else { i = 1; } } public void onScannedRobot (ScannedRobotEvent e) double a = e.getBearing(); double t = a * getEnergy(); } } A magic of register Every operation to anything must be done from register. Java has 4 registers to hold variable. The first one is this reference. The remaining register will be use for each parameter and variable inside method. Every type of variable use 1 register, except double use 2. In case of double come when 3 registers is already use by other variable, that double value will be place on an extra register. If you do any operation on any variable that do not on the register, Java will need to move that variable to the register before doing any of your operation, which cost codesize. This mean you should define a most-use variable before any other variables. Do this: public void onScannedRobot(ScannedRobotEvent e) { int int_variable_if_you_want; double bearing = e.getBearingRadians() + getHadingRadians(); double distance = e.getDistance(); // ... } Don't do this: public void onScannedRobot(ScannedRobotEvent e) { double distance = e.getDistance(); int int_variable_if_you_want; double bearing = e.getBearingRadians() + getHadingRadians(); // ... }

Cost Operation Cost in bytes creating a class 5 1st constructor free creating a method free returning from a method 1 calling a method 3 storing a local (non-register) variable 1 loading a local (non-register) variable 1 storing a static variable 2 loading a static variable 2 loading integer literals -1 to 5 1 loading integer literals -128 to 127 2 loading integer literals -32768 to 32767 3 loading other integer literals 2 loading double literals 0, 1 1 loading double literals -1, 2, 3, 4, 5 2 loading other double literals 3 loading string literals 2 declaring a variable free casting 1 promotion 1 arithmetic 1 ++ and -- (register or not) 1