How to add a letter the end of each word per its word index? [closed]

I have a problem about adding a letter the end of each word per its word index.

I cannot handle with that. How can I fix it?

Here is my code shown below.

for(int i=0;i<sentenceOfArray.length;i++) {
    sentenceOfArray[i] = sentenceOfArray[i] + "c";
}

Answer

Here is the solution with the usage of repeat method.

for(int i=0;i<sentenceOfArray.length;i++) {
    sentenceOfArray[i] = sentenceOfArray[i] + "a".repeat(i+1);
}