CS 180: Methods, Classes, and Arrays

Java classes include…

• Fields (attributes of an object or the class)

• Methods (operations on an object or the class)

Static field values

Same for all methods

Non-static field value

each object has its own

What are instance variables

non-static fields in a class declaration

What are class variables

Static fields in a class declaration

Local variables

variables in the method or block

Class variables

static fields in a class declaration

Instance variables

Non-static field in a class declaration

Parameters

variables in a method declaration

What is a method

A parameterized block of code that may return a value

Static method

• Can only access static fields and other static methods in the class

• Can be called using class name. i.e. Math.pow(2,5)

Non-static method

• May access non-static fields associated with the particular object

• Must be associated with an object, e.g., t3.describ()

• If no object is specified, “this” is implied

Methods are useful for…

• Reusability

• Readability

• Modularity

Method Syntax

return_type methodName(param_list) {
     statements;
     return; // If needed
}

Basic variable scope

Usable from the point of declaration to the end of the enclosing block

“Special” Variable scopes

• Parameters: accessible within the method body, can “hide” fields with the same name

• For loop variable: accessible within heading and body

this refers to…

the current object

Signature

the name and parameter types of a method/constructor