Java - checking if parseInt throws exception

Question

I m wondering how to do something only if Integer parseInt whatever  doesn t fail   More specifically I have a jTextArea of user specified values seperated by line breaks   I want to check each line to see if can be converted to an int   Figured something like this  but it doesn t work   for int i   0  i  lt  worlds jTextArea1 getLineCount    i                         if Integer parseInt worlds jTextArea1 getText worlds jTextArea1 getLineStartOffset i  worlds jTextArea1 getLineEndOffset i       null           Any help appreciated

User · Answer

instead of trying  amp  catching expressions   its better to run regex on the string to ensure that it is a valid number

User · Answer

You can use the try  catch statement in java  to capture an exception that may arise from Integer parseInt      Example   try     int i   Integer parseint stringToParse       parseInt succeded   catch Exception e         parseInt failed

User · Answer

Check if it is integer parseable  public boolean isInteger String string        try           Integer valueOf string           return true        catch  NumberFormatException e            return false            or use Scanner  Scanner scanner   new Scanner  Test string  12 3 dog 12345 cat 1 2E-3     while  scanner hasNext          if  scanner hasNextDouble              Double doubleValue   scanner nextDouble          else           String stringValue   scanner next              or use Regular Expression like  private static Pattern doublePattern   Pattern compile  -   d       d        public boolean isDouble String string        return doublePattern matcher string  matches

User · Answer

parseInt will throw NumberFormatException if it cannot parse the integer  So doing this will answer your question  try  Integer parseInt        catch NumberFormatException e     couldn t parse

User · Answer

public static boolean isParsable String input        try           Integer parseInt input           return true        catch  final NumberFormatException e            return false

User · Answer

It would be something like this   String text   textArea getText    Scanner reader   new Scanner text  useDelimiter   n    while reader hasNext        String line   reader next         try          Integer parseInt line             it worked           catch NumberFormatException e            it failed

User · Answer

You could try  NumberUtils isParsable yourInput    It is part of org apache commons lang3 math NumberUtils  and it checks whether the string can be parsed by Integer parseInt String   Long parseLong String   Float parseFloat String  or Double parseDouble String    See below   https   commons apache org proper commons-lang apidocs org apache commons lang3 math NumberUtils html isParsable-java lang String-

User · Answer

You can use a scanner instead of try-catch   Scanner scanner   new Scanner line  useDelimiter   n    if scanner hasNextInt         System out println  yes  it s an int

[java] Java - checking if parseInt throws exception

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