You should use a floating point type whenever you need a number with a decimal, such as 9.99 or 3.14515.
Float
The float data type can store fractional numbers from 3.4e−038 to 3.4e+038. Note that you should end the value with an "f":
Example
float myNum = 5.75f;
System.out.println(myNum);
Double
The double data type can store fractional numbers from 1.7e−308 to 1.7e+308. Note that you should end the value with a "d":
Example
double myNum = 19.99d;
System.out.println(myNum);
Use float or double?
The precision of a floating point value indicates how many digits the value can have after the decimal point. The precision of float is only six or seven decimal digits, while double variables have a precision of about 15 digits. Therefore it is safer to use double for most calculations.
Scientific Numbers
A floating point number can also be a scientific number with an "e" to indicate the power of 10:
Example
float f1 = 35e3f;
double d1 = 12E4d;
System.out.println(f1);
System.out.println(d1);
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