Retrieving the first digit of a number

Question

I am just learning Java and am trying to get my program to retrieve the first digit of a number - for example 543 should return 5  etc  I thought to convert to a string  but I am not sure how I can convert it back  Thanks for any help   int number   534  String numberString   Integer toString number   char firstLetterChar   numberString charAt 0   int firstDigit

User · Answer

Almost certainly more efficient than using Strings   int firstDigit int x        while  x  gt  9            x    10            return x       Works only for nonnegative integers

User · Answer

firstDigit   number   int  pow 10  int log number        This should get your first digit using math instead of strings   In your example log 543    2 73 which casted to an int is 2  pow 10  2    100 543 100   5 43 but since it s an int it gets truncated to 5

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int firstDigit   Integer parseInt Character toString firstLetterChar

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This way might makes more sense if you don t want to use str methods  int first   1  for  int i   10  i  lt  number  i    10        first   number   i

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int number   534      int firstDigit   Integer parseInt Integer toString number  substring 0  1

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Integer parseInt will take a string and return a int

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int number   534  String numberString        number  char firstLetterchar   numberString charAt 0   int firstDigit   Integer parseInt      firstLetterChar

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int number   534  int firstDigit   number 100           operator in java divide the numbers without considering the reminder so when we divide 534 by 100   it gives us  5      but if you want to get the last number   you can use     operator       int lastDigit   number 10     which gives us the reminder of the division   so 534 10   will yield the number 4

User · Answer

This example works for any double  not just positive integers and takes into account negative numbers or those less than one   For example  0 000053 would return 5   private static int getMostSignificantDigit double value        value   Math abs value       if  value    0  return 0      while  value  lt  1  value    10      char firstChar   String valueOf value  charAt 0       return Integer parseInt firstChar            To get the first digit  this sticks with String manipulation as it is far easier to read

[java] Retrieving the first digit of a number

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