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In this Java puzzle we pass a parameter to a constructor. I congratulate you if you can solve this puzzle!
Java puzzle 12: Passing a parameter to a constructor
Level: Hard
What is the output of this program and why?
public class MyClass { int x = 7; public MyClass() { x++; System.out.print(" n" + x); } public MyClass(int i) { x += i; System.out.print(" p" + x); } public int method(int i) { x += i; System.out.print(" s" + x); return x; } public static void main(String[] args) { new MyClass(new MyClass().method(3)); } }
Author: Sar Maroof
Answer explanation
- The statement new MyClass().method(3); instantiates an object from the class MyClass using the no-argument constructor.
The statement x++; increments the value of x by 1, x = 7+ 1 = 8. The statement System.out.print(” n” + x); writes n8 to the standard output. - The statement new MyClass().method(3) invokes the method and passes the value 3 to it. By passing the value 3, the statement x += i; increments the value of x by 3. The last value of x was 8. So, x = 8 + 3 = 11.
The statement System.out.print(” s” + x); writes s11 to the standard output. - The method method(3) returns 11 and we pass that value to a new object by using the statement new MyClass(new MyClass().method(3));
new MyClass(11) creates an object using the one-argument constructor.
The statement x += i; increments the value of x by i.
Don’t forget that this is a new object that is why the value of x is 7 + 11 = 18.
The statement System.out.print(” p” + x); writes p18 to the standard output.
The correct answer is: This program writes n8 s11 p18 to the standard output.
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