Jump to topic 1.1 Introduction to Algorithms, Programming, and Compilers 1.2 Variables and Data Types 1.3 Expressions and Output 1.4 Assignment Statements and Input 1.5 Casting and Range of Variables 1.6 Compound Assignment Operators 1.7 Application Program Interface (API) and Libraries 1.8 Documentation with Comments 1.9 Method Signatures 1.10 Calling Class Methods 1.11 Math Class 1.12 Objects: Instances of Classes 1.13 Object Creation and Storage (Instantiation) 1.14 Calling Instance Methods 1.15 String Manipulation 2.1 Algorithms with Selection and Repetition 2.2 Boolean Expressions 2.3 if Statements 2.4 Nested if Statements 2.5 Compound Boolean Expressions 2.6 Comparing Boolean Expressions 2.7 while Loops 2.8 for Loops 2.9 Implementing Selection and Iteration Algorithms 2.10 Implementing String Algorithms 2.11 Nested Iteration 2.12 Informal Run-Time Analysis 3.1 Abstraction and Program Design 3.2 Impact of Program Design 3.3 Anatomy of a Class 3.4 Constructors 3.5 Methods: How to Write Them 3.6 Methods: Passing and Returning References of an Object 3.7 Class Variables and Methods 3.8 Scope and Access 3.9 this Keyword 4.1 Ethical and Social Issues Around Data Collection 4.2 Introduction to Using Data Sets 4.3 Array Creation and Access 4.4 Array Traversals 4.5 Implementing Array Algorithms 4.6 Using Text Files 4.7 Wrapper Classes 4.8 ArrayList Methods 4.9 ArrayList Traversals 4.10 Implementing ArrayList Algorithms 4.11 2D Array Creation and Access 4.12 2D Array Traversals 4.13 Implementing 2D Array Algorithms 4.14 Searching Algorithms 4.15 Sorting Algorithms 4.16 Recursion 4.17 Recursive Searching and Sorting Big idea: Class methods (marked static) belong to the class itself, so you call them on the class name and no object is needed.
Learning objectives Develop code to call class methods and determine the result of those calls. Calling a static method A class method has static in its header. Call it with the class name and a dot: Math.sqrt(16), Integer.parseInt("42"). Inside the same class, you can drop the class name.
Code System .out.println(Tools .square(5 ));
System .out.println(Tools .sumSquares(2 , 3 ));Output 25
13 Tracing nested calls Evaluate the innermost call first, replace it with its return value, and work outward.
Code System .out.println(Tools .square(Tools .square(2 ) + 1 ));Output 25 Key points Class methods have static in the header and are called with ClassName.method(...). In the same class, the class name is optional. Watch out Calling a static method doesn't need an object, and it can't use instance variables directly (see 3.7). Quick check Is Math.abs(-3) a class method call or an instance method call? Show answer A class method call: it uses the class name Math, not an object.