Putting char into a java string for every 4 characters

Question

for example:

String str = "abc1234abcd12";
String str1 = "abc1234abcd1234abcd12";

adding a '-', after third char, and add '-', after every 4 char

how can I get this output:

String str = "abc-1234-abcd-12";
String str1 = "abc-1234-abcd-1234-abcd-12";

@Coldspeed No...he wants three characters in the very beginning, four in every other occurrence. — Tim Biegeleisen, Jun 25 '17 at 14:10
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this is a NOT a "write my program for me, send me teh codez" site. This should be down voted mercilessly and closed and everyone that answers this should be down voted into oblivion! Just wait until this type of person is your co-worked and you have to do all their work they get the money and credit and then end up your manager, you will be getting what you deserve! — , Jun 25 '17 at 14:41
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@JarrodRoberson I disagreed with you that no one should answer, until you mentioned the part about that person becoming my manager. This is exactly how I would describe most of my software managers actually; taking credit for others work. — Tim Biegeleisen, Jun 25 '17 at 14:44

score -1 · Answer 1 · answered Jun 25 '17 at 14:12

You can even get the formatting you want using a one-liner, q.v. the code snippet below. I manually build the first three characters followed a dash. After this, I do a blanket replacement to insert dashes after each subsequent group of four characters at at time. My code assumes that your string is at least three characters long. If you have logic for what happens for strings less than three characters of length, then update your question with that information.

String str1 = "abc1234abcd1234abcd12";
str1 = str1.substring(0, 3) + "-" + str1.substring(3).replaceAll("(.{4})", "$1-");
System.out.println(str1);

Output:

abc-1234-abcd-1234-abcd-12

Demo here:

Rextester

score -1 · Answer 2 · answered Jun 25 '17 at 14:38

This is the larger but better explainable solution for school ;).

String str = "abc1234abcd1234abcd12";
StringBuilder sb = new StringBuilder();
sb.append(str.substring(0,3));
for (int i = 3; i < str.length(); i = i + 4) {
    int start = i;
    int end = i + 4 > str.length() ? str.length() : i + 4;
    sb.append("-" + str.substring(start, end));
}
System.out.println(sb.toString());

score -2 · Answer 3 · answered Jun 25 '17 at 14:17

how can I get this output:...

It looks like you need to put a separator - to place apart a numbers from letter..

using java 8 can be as simple as:

String s = "abc1234abcd1234abcd12";
// split to numbers and letters using regex
String[] res = s.split("(?<=\\D)(?=\\d)|(?<=\\d)(?=\\D)");
// join that using the "-"
String finalResult = String.join("-", res);
System.out.println(finalResult);

the output:

abc-1234-abcd-1234-abcd-12

Putting char into a java string for every 4 characters

3 Answers3

Rextester