Java puzzle 18: Classes and objects

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If this program is compiled and run, it writes pp9 to the standard output.
Write only one statement at line 27. As a result of that statement the output of this code becomes 456. What is that statement?

Java puzzle 18: Classes and objects

Level: Hard

public class MC
  static String str = "p";
  static String str2 = "p";
  static int i = 9;
  MC(String str, String str2, int i)
    MC.str = str;
        || !str2.equals("5")
        || i != 6)
  public int mi(int i)
    MC.i = i;
    return i;
  String ms(String str)
    MC.str2 = str;
    return str2;
  public static void main(String[] args)
    // add your statement here!
    System.out.print(str + str2 + i);
Author: Sar Maroof

Answer explanation

  1. We need to reassign the values 456 to the variables str, str2 and i.
  2. By calling the constructor, we only can reassign the value of str.
  3. By invoking the method methodInt we can reassign the value of i.
  4. By invoking the method methodStr we can reassign the value of str2.
  5. By creating an object and passing the return values of the methods to the constructor we can invoke both methods with one statement.

The correct answer is:

new MC(“4”, new MC(“4”, “5”, 6).ms(“5”), new MC(“4”, “5”, 6).mi(6));

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Sar Maroof is graduated from HBO Amsterdam "higher professional education". He is a professional computer programming teacher, gives master classes and publishes technical articles. His experience with developing software started from 2001 and he has worked as a software developer for several big as well as small companies and later as a freelancer. He is the author of Java quizmaster and Build a Java application in 7 days.

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