Chapter 1: Java Programming Java is a high-level, class-based, object-oriented programming language widely used for web applications, mobile applications, and enterprise software. It is designed to be platform-independent through the Java Virtual Machine (JVM). A computer with a built-in compiler uses software to run computer-understandable language/ a set of instructions for output to be displayed in the console window.
Key Concepts: -Platform Independence: "Write once, run anywhere" via JVM. -Object-Oriented Programming: Encapsulation, inheritance, polymorphism, and abstraction.
- Syntax: Includes a structured set of rules for writing code in Java.
- Compilation and Execution: Java source code is compiled into bytecode, which is then executed by the JVM.
Chapter 2: Programming and Algorithms Programming in Java involves writing algorithms to solve problems efficiently.
Key Concepts: -Algorithm: A step-by-step procedure to perform a task or solve a problem. -Flow of Control: Refers to the order in which statements are executed in a program. -Efficiency: Algorithms are often evaluated by their time and space complexity.
Chapter 3a: if Statements
The if statement allows conditional execution of a block of code.
Syntax:
if (condition) {
// Code to execute if condition is true
}
- Condition: A Boolean expression that evaluates to `true` or `false`.
- Block Execution: The block is executed only if the condition is `true`.
Chapter 3b: if-else Statements
The `if-else` statement adds an alternative block of code to execute when the condition is false.
Syntax:
if (condition) {
// Code to execute if condition is true
} else {
// Code to execute if condition is false
}
- Provides a secondary path for when the condition is false.
Chapter 3c: Nested if Statements
Nested `if` statements allow multiple conditions to be checked sequentially within other `if` statements.
Syntax:
if (condition1) {
if (condition2) {
// Code for condition2 being true
}
}
- Useful for complex conditions that depend on multiple layers of logic.
Chapter 3d: if-Else-If Statements
The `if-else-if` statement chains multiple conditions, where each condition is checked sequentially.
Syntax:
if (condition1) {
// Code if condition1 is true
} else if (condition2) {
// Code if condition2 is true
} else {
// Code if all conditions are false
}
- Allows more granular control over conditional execution.
Chapter 3e: Switch Statements
The `switch` statement is used when multiple values of a variable are compared and different code needs to be executed for each case.
Syntax:
switch (expression) {
case value1:
// Code for value1
break;
case value2:
// Code for value2
break;
default:
// Default case
}
- Break: Prevents fall-through to the next case.
- Default: Executed when no case matches.
Chapter 3f: Relational and Logical Operators
Relational and logical operators are used to create conditions.
Relational Operators:
- `==`: Equal to
- `!=`: Not equal to
- `<`: Less than
- `>`: Greater than
- `<=`: Less than or equal to
- `>=`: Greater than or equal to
Logical Operators:
- `&&`: Logical AND
- `||`: Logical OR
- `!`: Logical NOT
Chapter 4a: While Loop
The `while` loop repeats a block of code as long as a condition is true.
Syntax:
while (condition) {
// Code to execute repeatedly
}
- Executes as long as the condition remains true.
Chapter 4b: Do While Loop
The `do-while` loop guarantees that the block of code is executed at least once, even if the condition is initially false.
Syntax:
do {
// Code to execute
} while (condition);
- The condition is checked after the code block is executed.
Chapter 4c: For Loop
The `for` loop is a control structure that allows you to repeat a block of code a certain number of times.
Syntax:
for (initialization; condition; update) {
// Code to execute repeatedly
}
- The loop is controlled by an initial value, condition, and an update step.
Chapter 4d: Nested Loops
A loop inside another loop is called a nested loop.
Syntax:
for (initialization; condition; update) {
for (initialization; condition; update) {
// Code to execute in nested loop
}
}
- Useful for multidimensional arrays or grid-based problems.
Chapter 5a: Methods
A method is a block of code that performs a specific task.
Syntax:
returnType methodName(parameters) {
// Code to execute
}
- Parameters: Inputs to the method.
- Return Type: The data type of the value the method returns.
Chapter 5b: Variable Scope
Scope defines the accessibility of variables.
- Local Scope: Variables declared inside a method.
- Instance Scope: Variables declared within a class but outside any method.
- Class Scope: Static variables shared among all instances of a class.
Chapter 6a: Classes and Objects
A class is a blueprint for objects. Objects are instances of a class.
Syntax:
class ClassName {
// Fields and methods
}
- Fields: Variables inside a class.
- Methods: Functions inside a class.
Chapter 6b: Instantiating Objects
Objects are created using the `new` keyword.
Syntax:
ClassName obj = new ClassName();Chapter 6c: Objects as Method Parameters and Return Types Methods can accept objects as parameters and return objects. Example: public void method(ClassName obj) { // Use obj }
Chapter 6d: Overloading Methods within a Class Overloading allows multiple methods in the same class with the same name but different parameters. Syntax: public void method(int a) { } public void method(String b) { }
Chapter 7a: Arrays An array is a collection of elements of the same type. Syntax: int[] arr = new int[5];
Chapter 7b: Searching Arrays
Arrays can be searched using loops or built-in methods like Arrays.binarySearch().
Chapter 7c: Useful Tricks for Arrays
- Sorting:
Arrays.sort() - Copying:
Arrays.copyOf() - Filling:
Arrays.fill()
Chapter 8a: Data Types Java has two types of data types:
- Primitive Types:
int,char,boolean, float - Reference Types: Arrays, Classes, Interfaces.
Chapter 8b: Strings Strings are immutable objects in Java. Syntax: String str = "Hello";
- String Methods:
.length(),.charAt(),.substring(), .
Chapter 9a: Inheritance Inheritance allows one class to inherit fields and methods from another. Syntax: class SubClass extends SuperClass { // Additional fields and methods }
Chapter 9b: Constructors in Inheritance A subclass inherits the constructor of its superclass but can override or extend it.
Chapter 9c: Overriding and Overloading Methods
- Overriding: Redefining a superclass method in a subclass.
- Overloading: Defining methods with the same name but different signatures in the same class.
Chapter 9d: Access Limitations and Multiple Inheritance
- Access Modifiers:
public,private,protected, and default. - Multiple Inheritance: Java does not support multiple inheritance of classes, but it allows multiple inheritance through interfaces.
Chapter 10: Polymorphism Polymorphism allows objects to be treated as instances of their superclass.
Chapter 11a: Abstraction Abstraction hides implementation details and shows only functionality. Syntax: abstract class ClassName { abstract void method(); }
Chapter 11b: Interfaces Interfaces provide a way to achieve abstraction and multiple inheritance. Syntax: interface InterfaceName { void method(); }