Double

Double Wrapper Class in Java

Overview

The Double class in Java is a wrapper class for the primitive double type. It provides utility methods to work with double-precision floating-point numbers and is part of the java.lang package.

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Key Features of the Double Wrapper Class

1. Boxing and Unboxing: Automatic conversion between primitive types and the Double wrapper class.
2. Constants: The class provides constants like MAX_VALUE, MIN_VALUE, POSITIVE_INFINITY, etc.
3. Utility Methods: Methods for parsing, converting, and performing mathematical operations on double values.

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Double Wrapper Class Operations

Arithmetic Operations

Operation	Symbol	Example
Addition	+	doubleValue + doubleValue
Subtraction	-	doubleValue - doubleValue
Multiplication	*	doubleValue * doubleValue
Division	/	doubleValue / doubleValue
Modulo	%	doubleValue % doubleValue

Relational Operations

Operation	Symbol	Example
Equal to	==	doubleValue == doubleValue
Not equal to	!=	doubleValue != doubleValue
Greater than	>	doubleValue > doubleValue
Less than	<	doubleValue < doubleValue
Greater than or equal to	>=	doubleValue >= doubleValue
Less than or equal to	<=	doubleValue <= doubleValue

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Static Methods

Method	Description	Example
compare(double d1, double d2)	Compares two double values.	Double.compare(3.2, 4.1) → Returns -1
parseDouble(String s)	Parses a String as a primitive double.	Double.parseDouble("3.14") → Returns 3.14
toHexString(double d)	Converts a double to its hexadecimal string representation.	Double.toHexString(3.14) → Returns "0x1.91eb86p1"
isNaN(double v)	Checks if the value is "Not-a-Number" (NaN).	Double.isNaN(Double.NaN) → Returns true
isInfinite(double v)	Checks if the value is infinite.	Double.isInfinite(Double.POSITIVE_INFINITY) → Returns true

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Instance Methods

Method	Description	Example
compareTo(Double anotherDouble)	Compares this Double object with another.	Double.valueOf(3.2).compareTo(Double.valueOf(4.1)) → Returns -1
equals(Object obj)	Checks if this object is equal to another.	Double.valueOf(3.2).equals(Double.valueOf(3.2)) → Returns true
isInfinite()	Checks if the value is infinite.	Double.valueOf(Double.POSITIVE_INFINITY).isInfinite() → Returns true
isNaN()	Checks if the value is "Not-a-Number" (NaN).	Double.valueOf(Double.NaN).isNaN() → Returns true
toString()	Returns a string representation of the value.	Double.valueOf(3.14).toString() → Returns "3.14"
hashCode()	Returns the hash code for the object.	Double.valueOf(3.14).hashCode()
byteValue()	Converts the Double value to a byte.	Double.valueOf(3.2).byteValue() → Returns 3
shortValue()	Converts the Double value to a short.	Double.valueOf(3.2).shortValue() → Returns 3
intValue()	Converts the Double value to an int.	Double.valueOf(3.2).intValue() → Returns 3
longValue()	Converts the Double value to a long.	Double.valueOf(3.2).longValue() → Returns 3L
doubleValue()	Returns the primitive double value of this Double object.	Double.valueOf(3.2).doubleValue() → Returns 3.2
floatValue()	Converts the Double value to a float.	Double.valueOf(3.2).floatValue() → Returns 3.2f

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Relational Operators and Their Equivalent Methods

Operator	Operator Usage	Equivalent Method	Usage
==	value1 == value2; // false	equals(Object)	Double.valueOf(value1).equals(value2); // false
!=	value1 != value2; // true	!equals(Object)	!Double.valueOf(value1).equals(value2); // true
<	value1 < value2; // true	compare(double, double)	Double.compare(value1, value2) < 0; // true
>	value1 > value2; // false	compare(double, double)	Double.compare(value1, value2) > 0; // false
<=	value1 <= value2; // true	compare(double, double)	Double.compare(value1, value2) <= 0; // true
>=	value1 >= value2; // false	compare(double, double)	Double.compare(value1, value2) >= 0; // false
+	double sum = value1 + value2;	N/A	Arithmetic operators are used directly; no equivalent method.
-	double diff = value1 - value2;	N/A	Arithmetic operators are used directly; no equivalent method.
*	double product = value1 * value2;	N/A	Arithmetic operators are used directly; no equivalent method.
/	double quotient = value1 / value2;	N/A	Arithmetic operators are used directly; no equivalent method.
%	double remainder = value1 % value2;	N/A	Arithmetic operators are used directly; no equivalent method.

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Example Code for Double Wrapper Class

public class DoubleWrapperExample {
    public static void main(String[] args) {
        // Double Examples
        Double doubleValue = Double.valueOf(3.14);
        System.out.println("Double as float: " + doubleValue.floatValue());
        System.out.println("Hexadecimal Representation (Double): " + Double.toHexString(3.14));

        // Comparing Doubles
        int compareResult = Double.compare(3.14, 2.5);
        System.out.println("Comparison Result (Double): " + compareResult);

        // Parsing Strings
        double parsedDouble = Double.parseDouble("2.71");
        System.out.println("Parsed Double: " + parsedDouble);

        // Converting Double to other types
        int intValue = doubleValue.intValue();
        System.out.println("Double as Int: " + intValue);
    }
}

For more: DoubleWrapperClass.java