Print All String Combinations Using Recursive function

Print all the possible combinations of a given String using Recursive function in Java

Here we’re using two recursive functions given the string is “abcd”:

1. substring is responsible for generating all possible substrings of given string in forward direction i.e. a, ab, abc, abcd, b, bc, bcd, c, cd, and d
2. permutation is responsible for generating all possible permutation of substring generated by substring() method of same length for e.g. possible permutation of abc is abc, acb, bac, bca, cab, and cba

public class PrintAllCombinationOfString {

	public static void main(String[] args) {
		String s = "abcd";
		for (int i = 0; i < s.length(); i++) {
			substring(s, "", i);
		}
	}
	
	public static void substring(String content, String part, int index) {
		if (index >= content.length()) {
			return;
		}
		String sub = part + content.charAt(index);

		permutation("", sub);

		substring(content, sub, index + 1);
	}

	private static void permutation(String prefix, String str) {
		int n = str.length();
		if (n == 0) {
			System.out.println(prefix);
		} else {
			for (int i = 0; i < n; i++) {
				permutation(prefix + str.charAt(i), str.substring(0, i) + str.substring(i + 1, n));
			}
		}
	}
}

Output
a
ab
ba
abc
acb
bac
bca
cab
cba
abcd
abdc
acbd
acdb
adbc
adcb
bacd
badc
bcad
bcda
bdac
bdca
cabd
cadb
cbad
cbda
cdab
cdba
dabc
dacb
dbac
dbca
dcab
dcba
b
bc
cb
bcd
bdc
cbd
cdb
dbc
dcb
c
cd
dc
d