/* package whatever; // don't place package name! */
 
import java.util.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String[][] array = { { "a", "b" }, { "c" } };
		StringJoiner sj = new StringJoiner(", ");
 
		for (String[] row : array) {
			for(String str: row){
				sj.add(str);
			}
		}
 
 
		String result = sj.toString();
		System.out.println(result);
	}
}

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