Reflection is a powerful feature in Java that allows you to inspect and manipulate classes, methods, and fields at runtime. It can be useful for various applications, including frameworks and libraries.
For a comprehensive guide on reflection, check out our article: Reflection in Java.
Java is a high-level, class-based, object-oriented programming language that is designed to have as few implementation dependencies as possible.
Java's main features include platform independence, object-oriented structure, and automatic memory management.
You can declare a variable in Java using the following syntax:
int number = 10;A constructor is a special method that is called when an object is instantiated. It initializes the object.
public class MyClass {
MyClass() {
// Constructor
}
}Inheritance is a mechanism where one class acquires the properties and behaviors of another class.
You can create a method in Java using the following syntax:
public void myMethod() {
// method body
}An interface is a reference type in Java, similar to a class, that can contain only constants, method signatures, default methods, static methods, and nested types.
You can implement an interface using the following syntax:
public class MyClass implements MyInterface {
// method implementations
}Polymorphism allows methods to do different things based on the object it is acting upon.
You can handle exceptions using try-catch blocks:
try {
// code that may throw an exception
} catch (Exception e) {
// handle exception
}The Java Collections Framework is a set of classes and interfaces that implement commonly reusable collection data structures.
You can create an ArrayList using the following syntax:
ArrayList list = new ArrayList<>(); ArrayList is backed by a dynamic array, while LinkedList is backed by a doubly linked list. ArrayList is faster for random access, while LinkedList is faster for insertions and deletions.
You can sort a list using the Collections.sort() method:
Collections.sort(list);A Stream is a sequence of elements supporting sequential and parallel aggregate operations.
You can create a Stream from a collection using the stream() method:
Stream stream = list.stream(); The 'final' keyword is used to declare constants, prevent method overriding, and prevent inheritance of classes.
You can create a thread by extending the Thread class or implementing the Runnable interface:
public class MyThread extends Thread {
public void run() {
// thread code
}
}'==' checks for reference equality, while '.equals()' checks for value equality.
A package is a namespace that organizes a set of related classes and interfaces.
You can create a package using the 'package' keyword:
package com.example.myapp;The JVM is an abstract machine that enables a computer to run Java programs by converting bytecode into machine code.
JDK (Java Development Kit) is for developing Java applications, JRE (Java Runtime Environment) is for running Java applications, and JVM (Java Virtual Machine) is the engine that executes Java bytecode.
You can read a file using FileReader and BufferedReader:
BufferedReader reader = new BufferedReader(new FileReader("file.txt"));
String line;
while ((line = reader.readLine()) != null) {
System.out.println(line);
}
reader.close();The 'this' keyword refers to the current object in a method or constructor.
You can create a HashMap using the following syntax:
HashMap map = new HashMap<>(); HashMap is not synchronized and allows null values, while Hashtable is synchronized and does not allow null values.
You can remove an element using the remove() method:
map.remove("key");A lambda expression is a concise way to represent an anonymous function that can be passed around.
You can use a lambda expression with functional interfaces:
Runnable r = () -> System.out.println("Hello, World!");The 'super' keyword is used to refer to the immediate parent class object.
You can create an enum using the following syntax:
public enum Day {
SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY
}The 'volatile' keyword indicates that a variable's value will be modified by different threads.
You can create a synchronized block using the following syntax:
synchronized (this) {
// synchronized code
}The 'static' keyword indicates that a variable or method belongs to the class rather than instances of the class.
You can create a static method using the following syntax:
public static void myStaticMethod() {
// method body
}The 'abstract' keyword is used to declare a class that cannot be instantiated or a method that must be implemented by subclasses.
You can create an abstract class using the following syntax:
public abstract class MyAbstractClass {
abstract void myAbstractMethod();
}The 'native' keyword indicates that a method is implemented in platform-specific code, typically in C or C++.
You can create a native method using the following syntax:
public native void myNativeMethod();The 'synchronized' keyword is used to control access to a block of code or an object by multiple threads.
You can create a synchronized method using the following syntax:
public synchronized void mySynchronizedMethod() {
// method body
}The 'throws' keyword is used in a method signature to declare that a method can throw exceptions.
You can declare a method that throws an exception using the following syntax:
public void myMethod() throws IOException {
// method body
}The 'try-with-resources' statement ensures that each resource is closed at the end of the statement.
You can use the 'try-with-resources' statement as follows:
try (BufferedReader reader = new BufferedReader(new FileReader("file.txt"))) {
// read file
}The 'instanceof' operator is used to test whether an object is an instance of a specific class or subclass.
You can use the 'instanceof' operator as follows:
if (obj instanceof MyClass) {
// obj is an instance of MyClass
}The 'default' keyword allows you to add new methods to interfaces without breaking existing implementations.
You can create a default method in an interface using the following syntax:
default void myDefaultMethod() {
// method body
}
Donate