class UserIdComparator implements Comparator<User> { public int compare(User user1, User user2) { if (user1.userId == user2.userId) { return 0; } else if (user1.userId > user2.userId) { return 1; } else { return -1; } } } We will now create a UsernameComparator class that establishes the comparison logic based on the username field. This class…
Read More Comparator interface in JavaOutput: true true true As you can see, the Car class inherits the Vehicle class, which is itself an instance of the Object class. Similarly, the Car class is an instance of both the Vehicle and the Object class. In Java, all classes inherit some useful methods from the Object class, which we will discuss…
Read More Object Class in Javapublic int sum(int a, int b, int c) { // body of the method } class Printer { // fields public void printBook(String bookName) { // … } public void printBook(String bookName, int numberOfPages) { // … } } class Printer { // fields public void printBook(String bookName) { // … } public String printBook(String…
Read More Method Overloading in JavaOutput: Brand is: Ford This is a Ford with a number of seats 5 and with colour blue
Read More Java Inheritance: A Beginner’s Guidepublic void methodName() { // code to be executed } public void methodName(int num, String data) { // code to be executed } methodName() methodName(10, “dataString”); class Test { public int sumNumbers(int a, int b) { int sum = a + b; return sum; } public static void main(String[] args) { int num1 = 10;…
Read More Methods in Javatype variableName = variableValue; public class Car { String brand; int maxSpeed; } class Car { String brand; int maxSpeed; public void printFields() { System.out.println(“BRAND: ” + brand); System.out.println(“MAX SPEED: ” + maxSpeed); } } public class Test { public static void main(String[] args) { Car ford = new Car(); ford.brand = “Ford”; ford.maxSpeed =…
Read More Variable in Javaclass Car { int numberOfSeats = 4; void addOneSeat(int numberOfSeats) { numberOfSeats = numberOfSeats + 1; // changes will only affect the local variable } public static void main(String args[]) { Car car = new Car(); System.out.println(“Number of seats before the change: ” + car.numberOfSeats); car.addOneSeat(car.numberOfSeats); System.out.println(“Number of seats after the change ” + car.numberOfSeats);…
Read More Java Pass-by-Value vs Pass-by-ReferenceIn addition to the Java Runtime Environment (JRE), the JDK includes the following components: Compiler The Java compiler is used to convert Java source code into bytecode that can be executed on the Java Virtual Machine (JVM). A compiler is a command-line tool that takes a .java file as input and produces a .class file…
Read More JRE, JDK, and JVM: Understanding Differences and UsesPrimitive type Wrapper class boolean Boolean byte Byte char Character float Float int Integer long Long short Short double Double class Test { int id = 5; Integer id1 = id; // autoboxing } class Test { public static void main(String[] args) { int a = 10; int b = 20; List<Integer> list = new…
Read More Autoboxing and Unboxing in Javabyte Uses 1 byte (8 bits) for a binary record of integers Values of this type are integers in the range -2 ^ 7 to 2 ^ 7-1, ie. [-128, 127] The default value is 0 Example: byte var1=120, byte var2=-30 short Uses 2 bytes (16 bits) to write integer binaries Values of this type…
Read More Java Data types1 public class HelloWorldClass { 2 3 public static void main(String[] args) { 4 System.out.println(“Hello World!”); 5 } 6 }
Read More How to Compile and Run your First Java Programclass Test { public static void main(String[] args) { short a = 10; int b = a; // automatically converts the short type into int type int c = 10; long d = c; // automatically converts the integer type into long type float f = d; // automatically converts the long type into float…
Read More Type Casting in Java