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  1. // Simple test to validate expression
  2. // Example: <number> <operator> <number> <=>
  3. //             1          *        5      =
  4.  
  5. import java.util.regex.Matcher;
  6. import java.util.regex.Pattern;
  7.  
  8. class ExpressionValidator
  9. {
  10. 	public static boolean isValidExpression( final String exp )
  11. 	{
  12. 		final String regex = "\\d+\\s*[*|/|+|-]\\s*\\d+\\s*[=]";
  13. 		final Pattern pattern = Pattern.compile( regex );
  14. 		final Matcher matcher = pattern.matcher( exp.trim() );
  15. 		return matcher.find();
  16. 	}
  17.  
  18. 	public static void main( final String[] args )
  19. 	{
  20. 		final String[] expressions = 
  21. 		{  
  22. 			" 1 +  2 =",
  23. 			" 3 *  5 =",
  24. 			"12 + 10 =",
  25. 			" 33 = 25 ",
  26. 			" +65  65 ",
  27. 			"45 666  ="
  28. 		};
  29.  
  30. 		for ( final String exp : expressions )
  31. 		{
  32. 			System.out.println( "[" + exp + "] >> " + isValidExpression( exp ) );
  33. 		}
  34. 	}
  35. }
Success #stdin #stdout 0.1s 27864KB
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Standard input is empty
stdout
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[ 1 +  2 =] >> true
[ 3 *  5 =] >> true
[12 + 10 =] >> true
[ 33 = 25 ] >> false
[ +65  65 ] >> false
[45 666  =] >> false
https://ideone.com/S9Wf9b
Java - Expression validator demo with regex
language:
Java (HotSpot 12)
created:
7 years ago
visibility:
public

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