Revision sheet: Java Programming Basics

📋 Course Outline

1. Java Program Structure
2. Java Data Type Categories
3. Primitive Data Types
4. Variables and Constants
5. Type Casting
6. Control Structures
7. Selection Structures

📖 1. Java Program Structure

🔑 Key Concepts & Definitions

• Java : A high-level, object-oriented programming language used to create robust, secure, and platform-independent applications.
• Class : A class is the basic unit of a Java program, and all Java code is grouped into classes.
• main() method : The main() method is the entry point of program execution, and a Java class can have only one main() method.

📝 Essential Points

• 🔄 A class definition follows this order:
  1. An access modifier such as public
  2. The keyword class
  3. The class name
  4. Opening and closing braces

💡 Memory Hook

Class → main() → statements

📖 2. Java Data Type Categories

📝 Essential Points

📌 Java data types have two main categories: primitive data types, such as int, double, char, and boolean, and reference data types, which include arrays, classes, and interfaces.

💡 Memory Hook

Primitive values versus reference objects

📖 3. Primitive Data Types

🔑 Key Concepts & Definitions

• boolean : A data type with only two possible values, true and false, used for simple flags that track true/false conditions.
• char : A data type that stores a single character, enclosed in single quotation marks in Java.

★ Must-know

• The int type is generally the default type for integral values unless memory space is a concern, while long is used when a wider range than int is needed.

• The double type is generally the default type for decimal values, while float is also used to save memory in large arrays of floating-point numbers.

Further detail

• The byte, short, and float types can help save memory space in large arrays.

📖 4. Variables and Constants

🔑 Key Concepts & Definitions

• Variable : A value that can change during program execution.
• Constant : Declared with the final keyword and unable to change value once assigned.

📝 Essential Points

📌 The syntax for a named constant is final data_type variable_name = value, and a named constant can be assigned a value only once.

💡 Memory Hook

Variable changes; constant stays fixed

📖 5. Type Casting

🔑 Key Concepts & Definitions

• Type casting : The conversion of a value from a specific type to a variable of another type; booleans cannot be converted to numeric types.

★ Must-know

📌 Widening conversion changes a lower-precision data type to a higher-precision type, is performed implicitly by the JVM, and causes no loss of information.

📌 Narrowing conversion changes a higher-precision data type to a lower-precision type and typically involves loss of information, so the programmer must use an explicit cast.

Further detail

• The explicit cast operator has the form $(data\_type\_name)\ expression$, where the expression is evaluated first and its value is then treated as the specified type.

• Casting the float value 6.82f to int with int a = (int) x; produces the integer value 6.

💡 Memory Hook

Widening preserves information; narrowing may lose it

📖 6. Control Structures

🔑 Key Concepts & Definitions

• Sequential structure : A sequential structure executes a sequence of statements in order.
• Control structures : Alternatives to sequential programs that alter the flow of execution.

📝 Essential Points

• The two control structures identified in the lesson are selection and repetition.

💡 Memory Hook

Sequential execution versus altered flow

📖 7. Selection Structures

🔑 Key Concepts & Definitions

• Selection structure : A structure that executes particular statements depending on a given condition and makes a choice in program flow.

★ Must-know

• Java provides three selection structures:
  • if
  • if...else
  • switch

Further detail

• A selection structure can determine whether a student passed or failed by evaluating a condition.