Java Type Casting

Type casting is when you assign a value of one primitive data type to another type.

In Java, there are two types of casting:

Widening Casting (automatically) - converting a smaller type to a larger type size
byte -> short -> char -> int -> long -> float -> double
Narrowing Casting (manually) - converting a larger type to a smaller size type
double -> float -> long -> int -> char -> short -> byte

Widening Casting

Widening casting is done automatically when passing a smaller size type to a larger size type:

Example

public class Main {
  public static void main(String[] args) {
    int myInt = 9;
    double myDouble = myInt; // Automatic casting: int to double

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

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Narrowing Casting

Narrowing casting must be done manually by placing the type in parentheses () in front of the value:

Example

public class Main {
  public static void main(String[] args) {
    double myDouble = 9.78d;
    int myInt = (int) myDouble; // Manual casting: double to int

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

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Real-Life Example

Here's a real-life example of type casting where we create a program to calculate the percentage of a user's score in relation to the maximum score in a game.

We use type casting to make sure that the result is a floating-point value, rather than an integer:

Example

// Set the maximum possible score in the game to 500
int maxScore = 500;

// The actual score of the user
int userScore = 423;

/* Calculate the percantage of the user's score in relation to the maximum available score.
Convert userScore to float to make sure that the division is accurate */
float percentage = (float) userScore / maxScore * 100.0f;

System.out.println("User's percentage is " + percentage);

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