Understanding Types Of Casting In Java

Introduction To Types Of Casting In Java

As a Java programmer, you’ll often find yourself needing to convert values between different Java data types. This process, known as type casting, is a fundamental part of working with data in Java and is something every Java programmer needs to understand. In this article, we’ll go through the process of type casting in Java, explore the two main types of casting – implicit and explicit, and learn when to use each one.

What Is Type Casting?

Type casting refers to converting a data type from one type to another. In Java, there are two types of data: primitive data types (byte, short, int, long, float, double, char, boolean) and non-primitive data types (classes, arrays, strings, etc.).

The conversion of data types allows for the operations between different data types and is a crucial part of many programming tasks. For instance, you might need to convert an integer into a float for mathematical operations, or perhaps convert a string into an integer to perform some calculation.

Implicit Type Casting (Widening Conversion) In Java

Implicit type casting, also known as automatic type casting or widening conversion, happens when the compiler automatically converts one data type to another without the programmer’s intervention. This happens when we assign a smaller data type to a larger data type.

For example, assigning an integer (which is 4 bytes) to a long (which is 8 bytes) or to a float (which is 4 bytes but can hold fractional values), the compiler automatically converts the integer to the long or float.

Here’s an example of implicit casting in Java:

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

System.out.println(myInt);      // Outputs 9
int myInt = 9;
double myDouble = myInt; // Automatic casting: int to double

System.out.println(myInt);      // Outputs 9
System.out.println(myDouble);   // Outputs 9.0

In the above example, Java automatically casts the integer value from myInt to a double when it’s assigned to myDouble.

Explicit Type Casting (Narrowing Conversion) In Java

Explicit type casting, or narrowing conversion, is when you manually convert a data type. This is necessary when you want to assign a larger data type to a smaller data type.

For instance, if you try to assign a double to an integer, the compiler will throw an error because a double is larger than an integer and can hold values an integer can’t represent. To do this, you’ll need to explicitly tell the compiler to make the conversion.

Here’s an example of explicit casting in Java:

double myDouble = 9.78;
int myInt = (int) myDouble; // Manual casting: double to int

System.out.println(myDouble);   // Outputs 9.78
System.out.println(myInt);      // Outputs 9

In the above example, we’ve manually cast myDouble to an integer by using (int). This tells the compiler we’re aware of the potential loss of data (the fractional part) and that we still want to make the conversion.

Casting Between Non-Primitive Data Types

Casting can also occur between non-primitive data types. In Java, all non-primitive types are subtypes of the Object class. A superclass reference variable can point to a subclass object. This is known as upcasting and is done implicitly.

Downcasting, on the other hand, is where a subclass reference variable points to a superclass object. This requires explicit casting.

For example:

Object myObject = new String("Hello");  // Upcasting (implicit)
String myString = (String) myObject;    // Downcasting (explicit)

In the above code, the Object class variable myObject is implicitly upcast to a String. To assign it back to a String variable, it needs to be explicitly downcast, which is done with (String).


Understanding type casting is essential for Java programming as it allows for flexibility in how we use our data. By knowing when and how to use implicit and explicit type casting, we can manipulate our data types to suit our needs, leading to more robust and adaptable code. Whether it’s converting between primitive data types or casting objects to different classes, mastering type casting will surely enhance your Java programming skills.

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