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    <p>To show what you can do when you split up the function in multiple parts I've created some code. Note that this not constitute a clear (class) design.</p> <p>This code has the advantages that you can actually <em>do</em> something with the values ones you parsed them. It is also useful to give good error messages. If you split up the <code>main</code> method even more, you can create a parser that validates values in real time as well (useful if you want to validate values within a GUI, for instance). </p> <pre><code>public class Numbers { private static final String[] s = new String[]{ "0",".",".0",".01","1.","1.0","1.01", "1 ","1 1","1/2","1/","1/0", "1 1/1", "1 0/0","1 /","1 /0", "1 0/"}; private static final Pattern FRACTION_PATTERN = Pattern.compile("(?:(\\d+)\\s+)?(\\d+)/(\\d+)"); public static void main(String[] args) { int counter = 0; for (String value : s) { counter++; String trimmedValue = value.trim(); if (isNumber(trimmedValue)) { System.out.printf("%d) %s ---- Natural number%n", counter, trimmedValue); continue; } boolean parseDecimal = isProbablyDecimal(trimmedValue); boolean parseFraction = isProbablyFraction(trimmedValue); if (parseDecimal &amp;&amp; parseFraction) { System.out.printf("%d) %s ---- Error (both decimal &amp; fraction)%n", counter, trimmedValue); continue; } if (parseDecimal) { if (!trimmedValue.matches("\\d*[.]\\d+")) { System.out.printf("%d) %s ---- Error (invalid decimal)%n", counter, trimmedValue); continue; } System.out.printf("%d) %s ---- Decimal value%n", counter, trimmedValue); continue; } if (parseFraction) { Matcher m = FRACTION_PATTERN.matcher(trimmedValue); if (!m.matches()) { System.out.printf("%d) %s ---- Error (invalid faction)%n", counter, trimmedValue); continue; } if (Integer.valueOf(m.group(3)) == 0) { System.out.printf("%d) %s ---- Error (division by zero in fraction)%n", counter, trimmedValue); continue; } if (m.group(1) != null) { System.out.printf("%d) %s ---- Mixed fraction%n", counter, trimmedValue); continue; } System.out.printf("%d) %s ---- Fraction%n", counter, trimmedValue); continue; } System.out.printf("%d) %s ---- Error (Cannot make bread out of it)%n", counter, trimmedValue); continue; } } public static boolean isNumber(String value) { return value.matches("\\d+"); } public static boolean isProbablyDecimal(String value) { // note, some countries use comma instead of dot return value.contains("."); } public static boolean isProbablyFraction(String value) { return value.contains("/"); } } </code></pre> <p>The output:</p> <pre class="lang-none prettyprint-override"><code>1) 0 ---- Natural number 2) . ---- Error (invalid decimal) 3) .0 ---- Decimal value 4) .01 ---- Decimal value 5) 1. ---- Error (invalid decimal) 6) 1.0 ---- Decimal value 7) 1.01 ---- Decimal value 8) 1 ---- Natural number 9) 1 1 ---- Error (Cannot make bread out of it) 10) 1/2 ---- Fraction 11) 1/ ---- Error (invalid faction) 12) 1/0 ---- Error (division by zero in fraction) 13) 1 1/1 ---- Mixed fraction 14) 1 0/0 ---- Error (division by zero in fraction) 15) 1 / ---- Error (invalid faction) 16) 1 /0 ---- Error (invalid faction) 17) 1 0/ ---- Error (invalid faction) </code></pre>
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    1. PODetermine if Decimal, Fraction or Invalid using Regex
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    1. USMaarten Bodewes
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    1. PODetermine if Decimal, Fraction or Invalid using Regex
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    1. COHint, you could also create a `Result` class, possibly with a `ResultType` enum with the values `RATIONAL`, `DECIMAL`, `FRACTION`, `MIXED_FRACTION` and - of course - `ERROR`. Normally you don't use exceptions for user input.
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