Java double type

In this chapter you will learn:

What is Java double type
How to create double type Literals
How to get the value of double infinity
What is double type NaN(Not a Number)

double type

double represents double-precision numbers. double is 64-bit width and its range is from 4.9e-324 to 1.8e+308 approximately.

Here is a program that uses double variables to compute the area of a circle:

public class Main {
  public static void main(String args[]) {
    double pi, r, a;
//from j a  v  a 2  s . c o  m
    r = 10.8888; // radius of circle
    pi = 3.1415926; // pi, approximately
    a = pi * r * r;

    System.out.println("Area of circle is " + a);
  }
}

The output:

double type Literals

double type numbers have decimal values with a fractional component. They can be expressed in either standard or scientific notation. Standard notation consists of a whole number component followed by a decimal point followed by a fractional component. For example, 2.0, 3.14159, and 0.6667.

public class Main { 
    public static void main(String args[]) { 
        double d =  3.14159; 
        System.out.print(d);//3.14159    
    } /* j  a v a2 s  .  c  o  m*/
}

Scientific notation uses a standard-notation, floating-point number plus a suffix that specifies a power of 10 by which the number is to be multiplied. The exponent is indicated by an E or e followed by a decimal number, which can be positive or negative. For example, 6.02E23, 314159E-05, and 4e+100.

public class Main {
  public static void main(String[] argv) {
    double d1 = 6.022E23;
    double d2 = 314159E-05;
    double d3 = 2e+100;
//  ja  v  a  2 s.c  om
    System.out.println("d1 is " + d1);
    System.out.println("d2 is " + d2);
    System.out.println("d3 is " + d3);
  }

}

The output generated by this program is shown here:

You can explicitly specify a double literal by appending a D or d.

public class Main { 
    public static void main(String args[]) { 
        double d =  3.14159D; 
        System.out.print(d);//3.14159    
    } /*from   j a va2  s  .  c o  m*/
}

Java's floating-point calculations are capable of returning +infinity, -infinity, +0.0, -0.0, and NaN

dividing a positive number by 0.0 returns +infinity. For example, System.out.println(1.0/0.0); outputs Infinity.

public class Main{
  public static void main(String[] args) {
    System.out.println(1.0/0.0);/* j ava  2  s.  c  om*/
  }

}

double Infinity

Dividing a negative number by 0.0 outputs -infinity. For example, System.out.println(-1.0/0.0); outputs -Infinity.

public class Main{
  public static void main(String[] args) {
    System.out.println(-1.0/0.0);/*from   j a v  a2s  . c om*/
  }

}

Output:

double NaN

Dividing 0.0 by 0.0 returns NaN. square root of a negative number is NaN. For example, System.out.println(0.0/0.0) and System.out.println(Math.sqrt(-1.0)) output NaN.

Dividing a positive number by +infinity outputs +0.0. For example, System.out.println(1.0/(1.0/0.0)); outputs +0.0.

Dividing a negative number by +infinity outputs -0.0. For example, System.out.println(-1.0/(1.0/0.0)); outputs -0.0.

public class Main {
  public static void main(String[] args) {
    Double d1 = new Double(+0.0);
    System.out.println(d1.doubleValue());
    /*  j  a  va 2  s.c  o  m*/
    Double d2 = new Double(-0.0);
    System.out.println(d2.doubleValue());
    System.out.println(d1.equals(d2));
    System.out.println(+0.0 == -0.0);

    
  }
}

The following code parses command-line arguments into double precision floating-point values

public class Main {
  public static void main(String[] args) {
    if (args.length != 3) {
      System.err.println("usage: java Main value1 op value2");
      System.err.println("op is one of +, -, *, or /");
      return;//from ja  v a  2 s  .co  m
    }
    try {
      double value1 = Double.parseDouble(args[0]);
      double value2 = Double.parseDouble(args[2]);
      if (args[1].equals("+")) {
        System.out.println(value1 + value2);
      } else if (args[1].equals("-")) {
        System.out.println(value1 - value2);
      } else if (args[1].equals("*")) {
        System.out.println(value1 * value2);
      } else if (args[1].equals("/")) {
        System.out.println(value1 / value2);
      } else {
        System.err.println("invalid operator: " + args[1]);
      }
    } catch (Exception nfe) {
      System.err.println("Bad number format: " + nfe.getMessage());
    }
  }
}

The Double class wraps a value of the primitive type double in an object. An object of type Double contains a single field whose type is double.

Double class provides several methods for converting a double to a String and a String to a double.

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