Fundamentals of Software Development 1Slide 1 Method invocation versus definition To define (write) a method means to write its codeTo define (write) a method means to write its code –The code is a recipe to follow when the method runs –Methods often have parameters – information that comes into the method when it is run To invoke (call, run) a method means to cause the method’s code to runTo invoke (call, run) a method means to cause the method’s code to run –Sending it actual values to substitute for the formal parameters of the method Example (on next slides)Example (on next slides)

Fundamentals of Software Development 1Slide 2 Method invocation versus definition To define (write) a method means to write its codeTo define (write) a method means to write its code To invoke (call, run) a method means to cause the method’s code to runTo invoke (call, run) a method means to cause the method’s code to run Example (on next slide):Example (on next slide): –The NameDropper class in the blue box defines: A field called myName to hold the NameDropper’s name to dropA field called myName to hold the NameDropper’s name to drop A constructor called NameDropper that takes the name to store in the fieldA constructor called NameDropper that takes the name to store in the field A method called transform that takes a phrase to tranformA method called transform that takes a phrase to tranform –The statements in the yellow box cause the NameDropper constructor and transform method to run They each run several times, with different actual arguments substituted for the formal parameters in the NameDropper definitionThey each run several times, with different actual arguments substituted for the formal parameters in the NameDropper definition These statements would themselves appear in some other classThese statements would themselves appear in some other class

Fundamentals of Software Development 1Slide 3 public class NameDropper extends StringTransformer implements StringTransformable { private String myName; Public NameDropper(String nameToUse) { this.myName = nameToUse; } public transform(String phrase) { return this.myName + “says ” + phrase; } NameDropper person1, person2, person3; person1 = new NameDropper(“Calvin”); person2 = new NameDropper(“Hobbes”); person3 = new NameDropper(“lobster”); person1.transform(“you look funny today, Hobbes.”); person2.transform(“you looker even funnier.”); person1.transform(“no, YOU look funnier.”); person3.transorm(“I amd just a lonely lobster.”); Definition of the NameDropper class Invoking the NameDropper constructor and transform method