Primitive Data Types

Double

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Like the int primitive data type, double is also very commonly used. Most of the time, you will use int for whole numbers and double for numbers with decimal points (rational or irrational). Double is also known as double-precision floating point. This means it has twice as many bits as float, meaning a double is more accurate than a float. Let's review the code below to see how double variables are declared and used.

DoubleDataTypeExample.java
package exlcode;

public class DoubleDataTypeExample {

  // double is any real number between -1.7E+308 and 1.7E+308
  public static double exampleVariableOne = 3.1415;
  public static double exampleVariableTwo = -0.002;
  public static double exampleVariableThree = 1.7E+250;

  public static void main(String[] args) {
    System.out.println(exampleVariableOne);
    System.out.println(exampleVariableTwo);
    System.out.println(exampleVariableThree);
  }
}

As with floats, doubles may have the character 'd' or 'D' at the end of the number to tell the program that the number is a double. Similar to a float datatype, the default value for double is "0.0". Doubles have one of the largest ranges of numbers compared to the other primitive data types.

Although a double is more accurate than float, it is still not recommended for currency as it is not precise enough to calculate strict numbers of this kind.

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Application Question

Which one of these is a valid double declaration?