Data type casting

In this chapter you will learn:

Compiler error for not compatible type
How to cast my type to another type

Not compatible type and casting

char and boolean are not compatible with each other.

public class Main {
  public static void main(String[] argv) {
    char ch = 'a';
    int num = 99;
    ch = num;//from   j  av a  2s  .  co m
  }
}

Compiling the code above will generate the following error message.

To make it work we have to add casting before the assignment.

public class Main {
  public static void main(String[] argv) {
    char ch = 'a';
    int num = 99;
    ch = (char)num;
  }/*from   j a va 2s  .co  m*/
}

Casting Incompatible Types

A narrowing conversion is to explicitly make the value narrower. A cast is an explicit type conversion. It has this general form:

(target-type) value

target-type specifies the desired type. The following code casts int type value to byte type value.

public class Main {
  public static void main(String[] argv) {
    int a = 1234;
    byte b;//from  j a v  a2  s  . c  om

    b = (byte) a;

    System.out.println("a is " + a);
    System.out.println("b is " + b);
  }
}

The output:

Truncation happens when assigning a floating-point value to an integer value. For example, if the value 1.23 is assigned to an integer, the resulting value will simply be 1.

public class Main {
/*j a  v  a2s  .c  o  m*/
  public static void main(String args[]) {
    byte b;
    int i = 1;
    double d = 1.123;

    System.out.println("Conversion of double to int.");
    i = (int) d;
    System.out.println("d: " + d + " i: " + i);

    System.out.println("Conversion of double to byte.");
    b = (byte) d;
    System.out.println("d: " + d + " b: " + b);

  }
}