Methods
click here for complete presentation on static methods
click here for complete presentation on objects
What is a method?
- A method is a piece of Java code packaged up so you can reuse it.
- Usually, a method will take some input and give some output
- System.out.println() is an example of a method
- Using a method (calling a method) always requires parentheses
Idea of a method
- Methods allow you to package up some code to run over and over
- Methods usually take some input (like numbers or Strings) so that they can be customized
- Methods often give back an answer (like the square root of a number)
Method Stucture
accessModifier returnType methodName(parameters)
Access Modifier
Access modifiers are either public, private, protected, or default
- public - Any program can use the method if it's public
- private - Only the class containing the method can use the method
- protected - Only classes in the same package can access the method. If the class is sub classed, then the method can be access regardless of the package.
- default - Default access occurs when you leave the access modifer blank.
Return Type
Methods can return primitives (int, double, boolean, char) ,objects, or void
- void - void method do not return a value. Void methods only do something. If you try to save the value they return, there will be a compiler error
- protected - Only classes in the same package can access the method. If the class is sub classed, then the method can be access regardless of the package.
- default - Default access occurs when you leave the access modifer blank.
Simple method example
Given two integers, find the bigger:
public int max(int a, int b)
{
return a;
else
return b;
}
Why Object Reference Methods
- object methods are methods connected to a particular object
- They perform a simple or specific task
Proper syntax for calling a static method gives first the reference variable (of the instance of class) , a dot, the name of the method, then the arguments
ObjectReferenceVariable.nameMethod(arg1, arg2, arg3);
Examples
String s1 = new String("Hello");
System.out.println("The lenght is " + s1.length());
output
The length is 5
Random gen = new Randon();
int num = gen.nextInt(10); //num contains 9
Simple static method example
Given two integers, find the smaller:
public static int min(int a, int b)
{
return a;
else
return b;
}
Why Static
- static methods are methods not connected to a particular object
- They perform a simple or specific task
Proper syntax for calling a static method gives first the name of the class the method is in, a dot, the name of the method, then the arguments
ClassName.MethodName(arg1, arg2, arg3);
Examples
int num = Math.abs(-3); // num is equal to 3
int high = Math.max(4,3); // high = 4
Scanner Class
Credit: A Slides are modified with permission from Barry Wittman at Elizabethtown College
This work is licensed under an Attribution-NonCommercial-ShareAlike 3.0 Unported License