Java Storing a Larger Number in a Smaller Number

Java Storing a Larger Number

in a Smaller Number

Problem

You have a number of a larger type and you want to store it in a variable of a smaller
type.

Solution

Cast the number to the smaller type. (A cast is a type listed in parentheses before a
value that causes the value to be treated as though it were of the listed type.)
For example, to cast a long to an int , you need a cast. To cast a double to a float ,
you also need a cast.

Explained

This causes newcomers some grief, as the default type for a number with a decimal
point is double , not float . So code like:

float f = 3.0;

won’t even compile! It’s as if you had written:

double tmp = 3.0;
float f = tmp;

You can fix it by making f a double , by making the 3.0 a float , by putting in a cast, or by assigning an integer value of 3:

double f = 3.0;
float f = 3.0f;
float f = 3f;
float f = (float)3.0;
float f = 3;

The same applies when storing an int into a short , char , or byte :

// CastNeeded.java
public static void main(String argv[]) {
int i;
double j = 2.75;
i = j;
// EXPECT COMPILE ERROR
i = (int)j;
// with cast; i gets 2
System.out.println("i =" + i);
byte b;
b = i;
// EXPECT COMPILE ERROR
b = (byte)i;
// with cast, i gets 2
System.out.println("b =" + b);
}

The lines marked EXPECT COMPILE ERROR do not compile unless either com- mented out or changed to be correct. The lines marked “with cast” show the correct forms.