Java String to Char Array

Question

String c="12345";
for(char k:c.toCharArray())
System.out.print(k+4);

This program outputs: 5354555657

I don't really understand why this is out putting those numbers. The only pattern I see is that it prints a "5" then takes the "1" from the string and adds 2 to make "3". Then prints a "5" then takes the "2" from the string and adds 2 to make "4" then prints a "5" and so on.

It prints 53|54|55|56|57. Just adds 4 to the ascii values of the respective characters. (for eg: "1" has ASCII of 49 => Add 4 => 53) — Vasan
– Vasan, Commented Mar 2, 2018 at 17:44
Each char can be treated as numeric value, representing its index in Unicode Table. Also in Java char + int = int which means that when we end up with '1'+4 it is evaluated as 49 (index of character '1') incremented by 4 which is 53. — Pshemo
– Pshemo, Commented Mar 2, 2018 at 17:49

rgettman · Accepted Answer · 2018-03-02 23:22:49Z

1

The characters in the array, when promoted to int for the addition of 4, take on their underlying Unicode value, of which the ASCII values are a subset. The digits 0-9 are represented by codes 48-57 respectively. Characters '1' through '5' are 49-53, then you add 4 and get 53-57.

After adding, cast the sum back to char so print can interpret it as a char.

System.out.print( (char) (k+4));

Output:

edited Mar 2, 2018 at 23:22

answered Mar 2, 2018 at 17:45

rgettman

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1 Comment

Troy Walker Over a year ago

Thank you, this makes sense. I appreciate the reply.

java-addict301 · Accepted Answer · 2018-03-02 17:50:10Z

0

This is because you're adding an int to a character (it's casting your character to an int and then adding it to 4, then printing it out).

You need to do:

System.out.println(Character.getNumericValue(k) + 4);

edited Mar 2, 2018 at 17:50

answered Mar 2, 2018 at 17:41

java-addict301

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4 Comments

Troy Walker Over a year ago

Awesome response! This is for a UIL question my kids are having on the written portion of Computer Science.

Troy Walker Over a year ago

The ASCII for k is 107 though, so I don't think I am following you.

Pshemo Over a year ago

@TroyWalker k is valuable holding as value characters like '1', '2', you need to look at their indexes.

java-addict301 Over a year ago

@TroyWalker - it's the ascii values for the numerical character, not k. For instance, 1 in ascii is 47, 2 is 48, etc (it's casting the char to an int). Adding those to the value of k gives you your output above.

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