Chapter 1 Java Programming Review

Introduction Java is platform-independent, meaning that you can write a program once and run it anywhere. Java programs can be embedded in HTML pages and downloaded by Web browsers to bring live animation and interaction to Web clients. Java source files end with the.java extension. Every class is compiled into a separate file bytecode that has the same name as the class and ends with the.class extension.

Introduction To compile a Java source code file, use the javac command. To run a Java class, use the java command. Every Java program is a set of class definitions. The keyword class introduces a class definition. The contents of the class are included in a block. A block begins with an opening brace “{“ and ends with the closing “}”. Methods are contained in a class. A Java application must have a main method. The main method is the entry point where the application program starts when it is executed.

Problem Solving Programming is a process of problem solving Problem-solving technique includes analyse the problem, outline the problem requirements, and design the steps (called algorithm). Three steps problem-solving process in the programming environment: –Analyse, outline the problem and its solution requirements. Design the algorithm to solve the problem. –Implement the algorithm uses any programming language and verify it. –Maintain or modify the program.

Primitive Data Types and Operations Four integer types (byte, short, int, long) that represent integers of four different sizes. Two floating-point types (float, double) that represent floating-point numbers of two different precisions. Character type (char) represents a single character All these called primitive data types. When they are declared, the variables of these types are created and assigned memory space.

Primitive Data Types and Operations Numeric operations: + (addition), - (substraction), * (multiplication), / (division), % (remainder). Increment operator (++), decrement operator (-- ). Casting – convert a value of one type into another type. Two types: widening and narrowing type. Three types of programming errors: syntax errors, runtime errors and logic errors.

Selection Statements Boolean types – represents a true or false value. Boolean operators - &&, &, ||, |, !, and ^. Relational operators -, >=. Selection statements are used for building selection steps into programs. Types: if, if…else, nested if, switch and conditional expressions. if statement – control decisions based on Boolean expression. switch statement – control decisions based on a switch expression. Keyword break is optional. Conditional expression – booleanExpression ? Expression1 : expression2;

Loop Statements while – checks the loop-continuation-condition first and then execute the loop body. do-while – execute the loop body first and then check the loop-continuation-condition. for – execute a loop body a predictable number of times. Has three parts: initialise a control variable, loop-continuation-condition, adjust the control variable. Keyword break – immediately ends the innermost loop and continue – only ends the current iterations.

Methods Method header specifies the modifiers, return value type, method name and parameters of the method. Example: public static int max (int num1, int num2) { …} A method may return a value or not (void). The arguments that are passed to a method should have the same number, type, and order as the parameters in the method definition.

Methods When a program calls a method, program control is transferred to the called method. A called method returns control to the caller when its return statement is executed or when its method-ending closing brace is reached. A method can be overloaded – two methods can have the same name as long as their method parameter lists differ. The scope of a local variable is limited locally to a method.

Arrays Syntax: dataType[ ] arrayRefVar or dataType arrayRefVar[ ] The declaration of an array variable does not allocate any space in memory for the array. An array variable contains a reference to an array. Elements can only be assigned to an array if it has already been created using new operator: new dataType[arraysize] myList

Arrays Each element in the array is represented using the syntax arrayRefVar[index]. An index must be an integer. After an array is created, its size becomes permanent and can be obtained using arrayRefVar.length Array initialiser – combines declaring an array, creating an array, and initialising in one statement: dataType[ ] arrayRefVar = {value0, value1, …, valuek);

Arrays Passing an array argument to a method is actually passing the reference of the array. Two-dimensional array: dataType[ ][ ] arrayRefVar or dataType arrayRefVar[ ][ ]