Double class is a wrapper class for the primitive type double which contains several methods to effectively deal with a double value like converting it to a string representation, and vice-versa. An object of Double class can hold a single double value. There are mainly two constructors to initialize a Double object-
Double(double b) :Creates a Double object initialized with the value provided.
Syntax : public Double(Double d)
Parameters :
d : value with which to initialize
Double(String s) :Creates a Double object initialized with the parsed double value provided by string representation. Defalut radix is taken to be 10.
Syntax : public Double(String s)
throws NumberFormatException
Parameters :
s : string representation of the byte value
Throws :
NumberFormatException : If the string provided does not represent any double value.
Methods:
toString() : Returns the string corresponding to the double value.
Syntax : public String toString(double b)
Parameters :
b : double value for which string representaion required.
valueOf() : returns the Double object initialised with the value provided.
Syntax : public static Double valueOf(double b)
Parameters :
b : a double value
Another overloaded function valueOf(String val) which provides function similar to
new Double(Double.parseDouble(val,10))
Syntax : public static Double valueOf(String s)
throws NumberFormatException
Parameters :
s : a String object to be parsed as double
Throws :
NumberFormatException : if String cannot be parsed to a double value in given radix.
parseDouble() : returns double value by parsing the string. Differs from valueOf() as it returns a primitive double value and valueOf() return Double object.
Syntax : public static double parseDouble(String val)
throws NumberFormatException
Parameters :
val : String representation of double
Throws :
NumberFormatException : if String cannot be parsed to a double value in given radix.
byteValue() : returns a byte value corresponding to this Double Object.
Syntax : public byte byteValue()
shortValue() : returns a short value corresponding to this Double Object.
Syntax : public short shortValue()
intValue() : returns a int value corresponding to this Double Object.
Syntax : public int intValue()
longValue() : returns a long value corresponding to this Double Object.
Syntax : public long longValue()
doubleValue() : returns a double value corresponding to this Double Object.
Syntax : public double doubleValue()
floatValue() : returns a float value corresponding to this Double Object.
Syntax : public float floatValue()
hashCode() : returns the hashcode corresponding to this Double Object.
Syntax : public int hashCode()
isNaN() : returns true if the double object in consideration is not a number, otherwise false.
Syntax : public boolean isNaN()
Another static method isNaN(double val) can be used if we dont need any object of double to be created. It provides similar functionality as the above version.
Syntax : public static boolean isNaN(double val)
Parameters :
val : double value to check for
isInfinite() : returns true if the double object in consideration is very large, otherwise false. Specifically any number beyond 0x7ff0000000000000L on positive side and below 0xfff0000000000000L on negative side are the infinity values.
Syntax : public boolean isInfinite()
Another static method isInfinite(double val) can be used if we dont need any object of double to be created. It provides similar functionality as the above version.
Syntax : public static boolean isInfinte(double val)
Parameters :
val : double value to check for
toHexString() : Returns the hexadecimal representation of the argument double value.
Syntax : public static String toHexString(double val)
Parameters :
val : double value to be represented as hex string
doubleToLongBits() : returns the IEEE 754 floating-point “double format” bit layout of the given double argument.
Syntax : public static long doubleToLongBits(double val)
Parameters :
val : double value to convert
doubleToRawLongBits() : returns the IEEE 754 floating-point “double format” bit layout of the given double argument. It differs from previous method as it preserves the Nan values.
Syntax : public static long doubleToRawLongBits(double val)
Parameters :
val : double value to convert
LongBitsToDouble() : Returns the double value corresponding to the long bit pattern of the argument. It does reverse work of the previous two methods.
Syntax : public static double LongBitsToDouble(long b)
Parameters :
b : long bit pattern
equals() : Used to compare the equality of two Double objects. This methods returns true if both the objects contains same double value. Should be used only if checking for equality. In all other cases compareTo method should be preferred.
Syntax : public boolean equals(Object obj)
Parameters :
obj : object to compare with
compareTo() : Used to compare two Double objects for numerical equality. This should be used when comparing two Double values for numerical equality as it would differentiate between less and greater values. Returns a value less than 0,0,value greater than 0 for less than,equal to and greater than.
Syntax : public int compareTo(Double b)
Parameters :
b : Double object to compare with
compare() : Used to compare two primitive double values for numerical equality. As it is a static method therefore it can be used without creating any object of Double.
Syntax : public static int compare(double x,double y)
Parameters :
x : double value
y : another double value
// Java program to illustrate
// various Double class methods
// of java.lang class
public class Double_test
{
public static void main(String[] args)
{
double b = 55.05;
String bb = "55";
// Construct two Double objects
Double x = new Double(b);
Double y = new Double(bb);
// toString()
System.out.println("toString(b) = " + Double.toString(b));
// valueOf()
// return Double object
Double z = Double.valueOf(b);
System.out.println("valueOf(b) = " + z);
z = Double.valueOf(bb);
System.out.println("ValueOf(bb) = " + z);
// parseDouble()
// return primitive double value
double zz = Double.parseDouble(bb);
System.out.println("parseDouble(bb) = " + zz);
System.out.println("bytevalue(x) = " + x.byteValue());
System.out.println("shortvalue(x) = " + x.shortValue());
System.out.println("intvalue(x) = " + x.intValue());
System.out.println("longvalue(x) = " + x.longValue());
System.out.println("doublevalue(x) = " + x.doubleValue());
System.out.println("floatvalue(x) = " + x.floatValue());
int hash = x.hashCode();
System.out.println("hashcode(x) = " + hash);
boolean eq = x.equals(y);
System.out.println("x.equals(y) = " + eq);
int e = Double.compare(x, y);
System.out.println("compare(x,y) = " + e);
int f = x.compareTo(y);
System.out.println("x.compareTo(y) = " + f);
Double d = Double.valueOf("1010.54789654123654");
System.out.println("isNaN(d) = " + d.isNaN());
System.out.println("Double.isNaN(45.12452) = " + Double.isNaN(45.12452));
// Double.POSITIVE_INFINITY stores
// the positive infinite value
d = Double.valueOf(Double.POSITIVE_INFINITY + 1);
System.out.println("Double.isInfinite(d) = " +
Double.isInfinite(d.doubleValue()));
double dd = 10245.21452;
System.out.println("Double.toString(dd) = " + Double.toHexString(dd));
long double_to_long = Double.doubleToLongBits(dd);
System.out.println("Double.doubleToLongBits(dd) = " + double_to_long);
double long_to_double = Double.longBitsToDouble(double_to_long);
System.out.println("Double.LongBitsToDouble(double_to_long) = " +
long_to_double);
}
}
Result :
toString(b) = 55.05
valueOf(b) = 55.05
ValueOf(bb) = 55.0
parseDouble(bb) = 55.0
bytevalue(x) = 55
shortvalue(x) = 55
intvalue(x) = 55
longvalue(x) = 55
doublevalue(x) = 55.05
floatvalue(x) = 55.05
hashcode(x) = 640540672
x.equals(y) = false
compare(x,y) = 1
x.compareTo(y) = 1
isNaN(d) = false
Double.isNaN(55.12452) = false
Double.isInfinite(d) = true
Double.toString(dd) = 0x1.4029b7564302bp13
Double.doubleToLongBits(dd) = 4666857980575363115
Double.LongBitsToDouble(double_to_long) = 10245.21452