Precision on a number format in Java

You can include a precision specifier to the following format specifiers −

%f
%e
%g
%s

On floating point, the number of decimal places is known.

Let’s say we declared a Formatter object −

Formatter f1 = new Formatter();

Now, we want 3 decimal places. For that, use 1.3f −

f1.format("%1.3f", 29292929.98765432);

The above will return the number with 3 decimal places −

29292929.988

The following is the final example −

Example

<span class="kwd">import</span><span class="pln"> java</span><span class="pun">.</span><span class="pln">util</span><span class="pun">.</span><span class="typ">Formatter</span><span class="pun">;</span>
<span class="kwd">public</span><span class="pln"> </span><span class="kwd">class</span><span class="pln"> </span><span class="typ">Demo</span><span class="pln"> </span><span class="pun">{</span>
<span class="kwd">    public</span><span class="pln"> </span><span class="kwd">static</span><span class="pln"> </span><span class="kwd">void</span><span class="pln"> main</span><span class="pun">(</span><span class="typ">String</span><span class="pln"> args</span><span class="pun">[])</span><span class="pln"> </span><span class="pun">{</span>
<span class="typ">       Formatter</span><span class="pln"> f1</span><span class="pun">,</span><span class="pln"> f2</span><span class="pun">,</span><span class="pln"> f3</span><span class="pun">;</span>
<span class="pln">       f1 </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">Formatter</span><span class="pun">();</span>
<span class="pln">       f1</span><span class="pun">.</span><span class="pln">format</span><span class="pun">(</span><span class="str">"%1.3f"</span><span class="pun">,</span><span class="pln"> </span><span class="lit">29292929.98765432</span><span class="pun">);</span>
<span class="typ">       System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="pln">f1</span><span class="pun">);</span>
<span class="pln">       f2 </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">Formatter</span><span class="pun">();</span>
<span class="pln">       f2</span><span class="pun">.</span><span class="pln">format</span><span class="pun">(</span><span class="str">"%1.7f"</span><span class="pun">,</span><span class="pln"> </span><span class="lit">29292929.98765432</span><span class="pun">);</span>
<span class="typ">       System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="pln">f2</span><span class="pun">);</span>
<span class="pln">       f3 </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">Formatter</span><span class="pun">();</span>
<span class="pln">       f3</span><span class="pun">.</span><span class="pln">format</span><span class="pun">(</span><span class="str">"%1.9f"</span><span class="pun">,</span><span class="pln"> </span><span class="lit">29292929.98765432</span><span class="pun">);</span>
<span class="typ">       System</span><span class="pun">.</span><span class="kwd">out</span><span class="pun">.</span><span class="pln">println</span><span class="pun">(</span><span class="pln">f3</span><span class="pun">);</span>
<span class="pun">    }</span>
<span class="pun">}</span>

Output

29292929.988
29292929.9876543
292929.987654320