Get int from String also containing letters in Java

Question

How can I get the int value from a string such as 423e - i e  a string that contains a number but also maybe a letter   Integer parseInt   fails since the string must be entirely a number

User · Answer

You can also use Scanner    Scanner s   new Scanner MyString   s nextInt

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Perhaps get the size of the string and loop through each character and call isDigit   on each character   If it is a digit  then add it to a string that only collects the numbers before calling Integer parseInt     Something like       String something    423e       int length   something length        String result           for  int i   0  i  lt  length  i              Character character   something charAt i           if  Character isDigit character                 result    character                      System out println  result is      result

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The NumberFormat class will only parse the string until it reaches a non-parseable character     Number NumberFormat getInstance   parse  123e    intValue     will hence return 123

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Just go through the string  building up an int as usual  but ignore non-number characters   int res   0  for  int i 0  i  lt  str length    i          char c   s charAt i       if  c  lt   0     c  gt   9   continue      res   res   10    c -  0

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Replace all non-digit with blank  the remaining string contains only digits   Integer parseInt s replaceAll     D           This will also remove non-digits inbetween digits  so  x1x1x  becomes 11   If you need to confirm that the string consists of a sequence of digits  at least one  possibly followed a letter  then use this   s matches     d   A-Za-z

User · Answer

Unless you re talking about base 16 numbers  for which there s a method to parse as Hex   you need to explicitly separate out the part that you are interested in  and then convert it  After all  what would be the semantics of something like 23e44e11d in base 10   Regular expressions could do the trick if you know for sure that you only have one number  Java has a built in regular expression parser    If  on the other hands  your goal is to concatenate all the digits and dump the alphas  then that is fairly straightforward to do by iterating character by character to build a string with StringBuilder  and then parsing that one

[java] Get int from String, also containing letters, in Java

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