Java Constructors

Question 1

Is there any compiler error in the below Java program? 

Java

class Point {
    int m_x, m_y; 
    public Point(int x, int y) {    m_x = x;    m_y = y;  }
    public static void main(String args[]) 
    {
      Point p = new Point();
    }
}

• Yes

• No

Question 2

JAVA

class Test
{
    static int a;
    
    static
    {
        a = 4;
        System.out.println (\"inside static block\\n\");
        System.out.println (\"a = \" + a);
    }
    
    Test()
    {
        System.out.println (\"\\ninside constructor\\n\");
        a = 10;
    }
    
    public static void func()
    {
        a = a + 1;
        System.out.println (\"a = \" + a);
    }
    
    public static void main(String[] args)
    {

        Test obj = new Test();
        obj.func();

    }
}
 

• inside static block
  a = 4
  inside constructor
  a = 11

• Compiler Error
• Run Time Error
• inside static block
  a = 4
  inside constructor
  a = 5
  

• inside static block
  a = 10
  inside constructor
  a = 11
  

Question 3

Java

final class Complex {
    private  double re,  im;
    public Complex(double re, double im) {
        this.re = re;
        this.im = im;
    }
    Complex(Complex c)
    {
      System.out.println(\"Copy constructor called\");
      re = c.re;
      im = c.im;
    }            
    public String toString() {
        return \"(\" + re + \" + \" + im + \"i)\";
    }            
}
class Main {
    public static void main(String[] args) {
        Complex c1 = new Complex(10, 15);
        Complex c2 = new Complex(c1);    
        Complex c3 = c1;  
        System.out.println(c2);
    }
}

• Copy constructor called
  (10.0 + 15.0i)

• Copy constructor called
  (0.0 + 0.0i)

• (10.0 + 15.0i)

• (0.0 + 0.0i)

Question 4

Output of following Java program

Java

class Point {
  int m_x, m_y;
  
  public Point(int x, int y) { m_x = x; m_y = y; }
  public Point() { this(10, 10); }
  public int getX() { return m_x; }
  public int getY() { return m_y; }
  
  public static void main(String args[]) {
    Point p = new Point();
    System.out.println(p.getX());
  }
} 

• 10
• 0
• compiler error

Question 5

Which of the following is/are true about constructors in Java?

1) Constructor name should be same as class name.
2) If you don\'t define a constructor for a class, 
    a default parameterless constructor is automatically
    created by the compiler. 
3) The default constructor calls super() and initializes all 
   instance variables to default value like 0, null.
4) If we want to parent class constructor, it must be called in 
   first line of constructor.

• 1
• 1, 2
• 1, 2 and 3
• 1, 2, 3 and 4

Question 6

Predict the output?

Java

package main;
class T {
  int t = 20;
}
class Main {
   public static void main(String args[]) {
      T t1 = new T();
      System.out.println(t1.t);
   }
}

• 20
• 0
• Compiler Error

Question 7

Predict the output of following Java program

Java

class T {
  int t = 20;
  T() {
    t = 40;
  }
}
class Main {
   public static void main(String args[]) {
      T t1 = new T();
      System.out.println(t1.t);
   }
}

• 20
• 40
• Compiler Error