英文java 讲义lecture13-methodsandreview.pdfVIP

Schedule • Quiz #2 (in lab) today • Midterm (in class, 1.5 hours) Wednesday October 12th – Note: Follows a Monday schedule • Assignment 2 posted Today • Methods • Review Methods What is a method? • A method is a block of code that defines a sequence of programming statements that perform an action • it can take in input parameters • it can return a result • The idea is to “bundle” everything together into one single command. • Example – double Math.pow (double a, double b) – takes double arguments, returns a doublewhich is the value of the first argument raised to the power of the second argument Why use methods • We don’t always have to code the functionality ourselves • Even if we do need to code it, we can write it just once and then “forget” about it. • We don’t care how it was coded, as long as it functions correctly (accurate, efficient, …) • We just need to know the interface to use it – what do we pass to it – what does it return – e.g., Math.pow, System.out.println Why modularize? • Real systems are too complex to be 1 monolithic main method • divide-and-conquer approach – break problem into smaller ones • improves understandability • improves code reuse – never want to be copy and paste a lot of code Example: Printing a box public class BoxPrint { public static void main(String[] args) { System.out.println(*****); System.out.println(* *); System.out.println(* *); System.out.println(* *); System.out.println(*****); // What if I want to do this many times? } } New commands For now, all I can do is copy/paste. A