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Topics

Java Basics

Introduction to JavaInstalling JavaJava SyntaxJava CommentsJava VariablesJava Data TypesJava Type CastingJava OperatorsJava StringsJava MathJava BooleansJava If...ElseJava SwitchJava While LoopJava For LoopJava Break/ContinueJava Arrays

Java OOP

Java Classes/ObjectsJava Class AttributesJava Class MethodsJava ConstructorsJava ModifiersJava EncapsulationJava PackagesJava InheritanceJava PolymorphismJava Inner ClassesJava AbstractionJava InterfaceJava Enums

Java Advanced

Java ExceptionsJava Regular ExpressionsJava ThreadsJava LambdaJava File HandlingJava Read FilesJava Write/Create FilesJava Delete Files

Java Data Structures

Java LinkedListJava ArrayListJava HashMapJava HashSetJava IteratorJava Wrapper Classes

Java I/O

Java InputJava OutputJava ScannerJava BufferedReaderJava PrintWriter

Java Generics

Java Generic MethodsJava Generic ClassesJava Bounded Type ParametersJava Wildcard Generics

Java Collections

Java List InterfaceJava Set InterfaceJava Queue InterfaceJava Deque InterfaceJava Map Interface

Java Concurrency

Java MultithreadingJava SynchronizationJava Thread PoolJava Callable and FutureJava Locks

Java Networking

Java SocketsJava URL ProcessingJava DatagramsJava Networking Classes

Java Database

Java JDBCJava Database ConnectivityJava SQL QueriesJava Prepared Statements

Java GUI

Java AWTJava SwingJava JavaFXJava Event Handling

Java Testing

Java JUnitJava TestNGJava MockitoJava Assertions

Java Build Tools

Java MavenJava GradleJava Ant

Java Best Practices

Java Coding ConventionsJava Design PatternsJava Performance OptimizationJava Security

Java Data Types

Java data types are essential components of the language that define the kind of values a variable can hold. Understanding these types is crucial for efficient programming and memory management in Java applications.

Primitive Data Types

Java has eight primitive data types, which are the building blocks for object creation. These types are:

  • byte: 8-bit signed two's complement integer
  • short: 16-bit signed two's complement integer
  • int: 32-bit signed two's complement integer
  • long: 64-bit signed two's complement integer
  • float: 32-bit IEEE 754 floating-point
  • double: 64-bit IEEE 754 floating-point
  • boolean: true or false
  • char: 16-bit Unicode character

Example of Primitive Data Types


int age = 25;
double salary = 50000.50;
boolean isEmployed = true;
char grade = 'A';

Reference Data Types

Reference data types are used to store complex values, such as objects. The most common reference type is the String, which stores text.

Example of Reference Data Types


String name = "John Doe";
int[] numbers = {1, 2, 3, 4, 5};

Type Casting

Type casting is the process of converting one data type to another. Java supports two types of casting:

  • Widening Casting (Automatic): Converting a smaller type to a larger type size
  • Narrowing Casting (Manual): Converting a larger type to a smaller size type

Example of Type Casting


// Widening Casting
int myInt = 9;
double myDouble = myInt; // Automatic casting: int to double

// Narrowing Casting
double myDouble2 = 9.78;
int myInt2 = (int) myDouble2; // Manual casting: double to int

Best Practices

  • Choose the appropriate data type based on the value range and precision required.
  • Use int for whole numbers and double for decimal numbers in most cases.
  • Prefer StringBuilder over String for mutable strings to improve performance.
  • Be cautious when using type casting to avoid data loss or unexpected behavior.
  • Utilize wrapper classes (e.g., Integer, Double) when working with collections or generics.

Conclusion

Mastering Java data types is fundamental to writing efficient and error-free code. By understanding the differences between primitive and reference types, as well as proper type casting techniques, developers can create robust Java applications. Remember to choose the appropriate data type for each variable to optimize memory usage and performance.