If you run the following program and enter the character “a” at the first prompt

Question

If you run the following program and enter the character “a” at the first prompt and the character “b” at the second prompt the message “a not = b” will appear. However if you run it again and enter the character “a” at both prompts, it will also print the message “a not = a”. Explain why in detail and explain how to re-code to correct it.

public class BadStringCompare public static void main(Stringl] args) Scanner keyboard- new Scanner(System.in); System.out.println("Enter first letter..."); String string1- keyboard.nextLine(); System.out.println("Enter second letter..."); String string2 keyboard.nextLine); if (string1 string2) System.out.println (string1-"string2); else System.out.println (string1 " notstring2);

Explanation / Answer

Explanation:

== operator is a reference comparison, i.e. both objects point to the same memory location
.equals() method evaluates to the comparison of values in the objects

BadStringCompare.java

import java.util.Scanner;

public class BadStringCompare {

public static void main(String[] args) {

Scanner keyboard = new Scanner(System.in);

System.out.println("Enter first letter: ");

String string1 = keyboard.nextLine();

System.out.println("Enter second letter: ");

String string2 = keyboard.nextLine();

if(string1.equals(string2)) {

System.out.println(string1+" = "+string2);

} else {

System.out.println(string1+" not = "+string2);

}

}

}

Output:

Enter first letter:
a
Enter second letter:
a
a = a

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