How to Format the Width of Floats in Java

You can format floating-point Java values to any given width.

The "float" type is one of the primitive types in the Java programming language. A float variable contains a single-precision, floating point value that has an integer part and a decimal expansion. By using built-in Java library functions, Java applications can format a float value to have a given width (that is, a given number of places) when output to a stream or a file. These capabilities are useful to generate neat tables where all numbers are lined up in columns, or to satisfy application-dependent requirements (e.g., dollar amounts formatted to two decimal places representing cents).

Instructions

1. Include the following line at the beginning of your Java code:

   import java.util.*;

2. Create an instance of the built-in Formatter class, as in the following sample code:

   Formatter myFormatter = new Formatter();

3. Format a float value into whatever format you need, as in the following sample code:

   float myFloat = 46.301;

   myFormatter.format("%7.2f",myFloat);

   System.out.println(myFormatter);

   The example will format the number for seven places, of which two are after the decimal period. The period counts as one place. The number is left-justified, with spaces added if there are fewer digits than places. Therefore, the sample float value will be formatted as " 46.30" with two spaces before the digit "4". The "Format String Syntax" Web page explains all other possible ways of formatting a float to a given width in Java.

References

• Oracle: Java: Class Formatter (Format String Syntax)