public class StringTest {
    public static void main(String[] argv) {
        String s="";
        Runtime rt = Runtime.getRuntime();
        long startMemory = 0;
        long startTime = 0;

        startMemory = rt.freeMemory();
        startTime = System.currentTimeMillis();

        for (int i = 0; i < 10000; i++) {
           s += ("ab");;
        }

        long endMemory = rt.freeMemory();
        long endTime = System.currentTimeMillis();
    
        System.out.println("Elapsed time: " + (endTime - startTime)+ " ms");
        System.out.println("Memory usage: " + (startMemory - endMemory) + " bytes");
    }
}