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Problem of the Day

Tuesday, February 17, 2026

Problem:

The class DefaultDemo is shown here.

public class DefaultDemo
{
    // instance variables
    private int p;
    private String q;

    public DefaultDemo()
    {
        // instance variables use default values 
        // from declaration above
        System.out.println(p + "," + q);
    }

    public void aMethod()
    {
        // local variables
        int r;
        String s;
        // local variables use default values
        // from declaration above
        System.out.println(r + "," + s);    
    }
}

What compilation issues(s), if any, are present in this code?

  1. Variables p, q, r, and s haven't been initialized
  2. Variables p and q haven't been initialized
  3. Variables r and s haven't been initialized
  4. There are no compilation errors in this code.

Show solution:

The correct answer is c. Instance variables such as p and q in this example, have default values assigned if they aren't explicitly initialized with another value. Local variables such as r and s require explicit initialization before they can be used. When this code is compiled, those variables cause a variable might not have been initialized error.