Java implementation of string permutation and combination

This paper introduces the string arrangement and combination in Java for your reference. The specific contents are as follows

Combination:

Either select the first character in the string with length N, and then select M-1 characters in the other strings with length n-1, or do not select the first character in the string with length N, and then select M characters in the other strings with length n-1

The above is the whole content of this article. I hope it will be helpful to your study, and I hope you can support programming tips.