To remove the ", " part which is immediately followed by end of string, you can do:

str = str.replaceAll(", $", "");

This handles the empty list (empty string) gracefully, as opposed to lastIndexOf / substring solutions which requires special treatment of such case.

Example code:

String str = "kushalhs, mayurvm, narendrabz, ";
str = str.replaceAll(", $", "");
System.out.println(str);  // prints "kushalhs, mayurvm, narendrabz"

NOTE: Since there has been some comments and suggested edits about the ", $" part: The expression should match the trailing part that you want to remove.

• If your input looks like "a,b,c,", use ",$".
• If your input looks like "a, b, c, ", use ", $".
• If your input looks like "a , b , c , ", use " , $".

I think you get the point.

One may use string utility methods such as StringUtil.join to concatenate elements in an array or a collection object. Consult the StringUtil API's StringUtil.join entry.

For example:

StringUtils.join(["a", "b", "c"], "--")  // => "a--b--c"

You could try a regular expression:

names = names.replaceAll(",$", "");

Or a simple substring:

if (names.endsWith(",")) {
  names = names.substring(0, names.length() - 1);
}

I often use this idiom for this problem -- make a variable comma special ("") for the first time, and then restore it to the normal state (", ") for the second time and onward:

public void print() {
    for(int i = 0; i < M.length; i++){
        String comma = "";      // first time special
        for(int j = 0; j < M[i].length; j++){
            System.out.print(comma + M[i][j]);
            comma = ",";        // second time onward
        }
        System.out.println();
    }

}

Many ways.

1. Use a StringBuilder to make your string, then after the loop, if it is not empty, lop off the last character (sb.setLength(sb.length() - 1)).

2. Use a boolean to track if this is the first time through the loop. If yes, just print the number. If not, print a comma, then the number. Set the boolean to false after.

3. Use string joining:

List<String> items = List.of("Hello", "World!");
System.out.println(String.join(", ", items));

String start = "A,B,C,";
String result = start.subString(0, start.lastIndexOf(',', start.lastIndexOf(',') - 1));

Acrually it is better to use JSON library to construct the object. In this case you can do it like this:

if (itr_1.hasNext()) {
    jsonUIResponse.append("},");
} else {
    jsonUIResponse.append("}");
}

The trialing comma is ignored, see the JLS - 10.6. Array Initializers:

An array initializer is written as a comma-separated list of expressions, enclosed by braces { and }.

A trailing comma may appear after the last expression in an array initializer and is ignored.

It's useful when you want to initialize long list (some people find it more readable):

String[] myList = {
                   "hello",
                   "Mr",
                   "How",
                   "are",
                   "You",
                   "I'm",
                   "fine",
                   "thank",
                   "you",
                  };

You have no way to remove it programmatically unless you iterate on the source file.

You could remove the last character if every line as the comma:

resultString = resultString.substring(0, resultString.length()-1)