Java Type Conversion

Summary: in this tutorial, you’ll learn about Java type conversion which allows you to convert a value of one type to another.

Introduction to Java type conversion

Java has a number of different primitive types. For example, integer types include byte, short, int, and long. Sometimes, you need to convert a value of one type to another.

Generally speaking, type conversion has two broad categories:

Implicit type conversion
Explicit type conversion

Implicit type conversion

Implicit type conversion occurs when you convert a value of a type with a smaller range to a value of a type with a larger range. Implicit type conversion is performed automatically by the Java compiler.

If you convert a value of type from left to right, you need to perform an explicit type conversion:

byte -> short -> char -> int -> long -> float -> double

For example:

int count = 1;
long countBig = count;Code language: Java (java)

In this example:

First, define a variable count with type int and initialize its value to 1.
Second, define another variable countBig with the type long and assign the value of the count variable to it.

Because the type of the count is int and countBig is long, the Java compiler automatically converts the value of the count variable to long and assigns it to the countBig variable.

The implicit type conversion is also known as implicit casting or widening casting. Java allows this type of conversion because it doesn’t result in any data loss.

Explicit type conversion

Explicit type conversion occurs when you convert a value of one type with a larger range to another type with a smaller range.

The explicit type conversion is also known as explicit casting or narrowing casting. Because the explicit type conversion may result in data loss or truncation of value, Java requires a cast operator.

If you convert a value of type from left to right, you need to perform an explicit type conversion:

double -> float -> long -> int -> char -> short -> byte

The syntax for explicit type conversion is as follows:

targetType variable = (targetType)anotherVariable;Code language: Java (java)

In this syntax, the (targetType) is the cast operator. For example:

long countBig = 1;
int count = (int) countBig;Code language: Java (java)

In this example:

First, define a variable countBig with type long and initialize its value to 1.
Second, define another variable count with the type int and assign the value of the countBig variable to the count variable.

The (int) is the cast operator that converts the value of the long type to a value of the int type.

Java type conversion examples

Let’s take some examples of using type conversions in Java.

1) Using an explicit type conversion that doesn’t cause data loss

public class App {
    public static void main(String[] args) {
      int x = 10;
      long y = 20;
      int z = x + y; // error
      System.out.println(z);
    }
}Code language: Java (java)

In this example:

First, define two variables x with type int and y with type long.
Second, define another variable z with type int, add the values of x and y, and assign the result to the z variable.

Because we sum an int to a long values, the result will have the type long. However, since we assign a value of type long to a variable of type int, the program won’t be compiled.

To make it work, you need to change the type of the variable z to long or perform an explicit type conversion:

public class App {
    public static void main(String[] args) {
      int x = 10;
      long y = 20;
      int z = (int)(x + y);
      System.out.println(z);
    }
}Code language: Java (java)

2) Using an explicit type conversion that causes a truncation of value

The following example shows how to explicitly convert a value of the float type to a value of the int type which results in data loss:

public class App {
    public static void main(String[] args) {
        double price = 10.99;
        int price2 = (int)price;
        System.out.println(price2);
    }
}Code language: Java (java)

In this example:

First, define the variable price with type double and initialize its value to 10.99.
Second, define another variable price2 with the type int and assign the value of the price variable to it.

Since the type of the price has a larger range than the type of the price2, we need to use the cast operator (int).

In this example, the (int) operator truncates the fractional part of the value of the price variable.

Summary

Java type conversion allows you to convert a value of one type to another.
Java has explicit type conversion (widening cast) and implicit type conversion (narrowing cast).
Widening conversion is safe and automatic because it doesn’t cause any data loss while the narrowing conversion should be done with care to ensure that data loss is acceptable in your specific use case.