Java Programming - Java.lang Class

Exercise : Java.lang Class - Finding the output
26.
What will be the output of the program?
public class Test 
{ 
    public static void main(String[] args) 
    {
        final StringBuffer a = new StringBuffer(); 
        final StringBuffer b = new StringBuffer(); 

        new Thread() 
        { 
            public void run() 
            {
                System.out.print(a.append("A")); 
                synchronized(b) 
                { 
                    System.out.print(b.append("B")); 
                } 
            } 
        }.start(); 
            
        new Thread() 
        {
            public void run() 
            {
                System.out.print(b.append("C")); 
                synchronized(a) 
                {
                    System.out.print(a.append("D")); 
                } 
            } 
        }.start(); 
    } 
}
ACCBAD
ABBCAD
CDDACB
Indeterminate output
Answer: Option
Explanation:

It gives different output while executing the same compiled code at different times.

C:\>javac Test.java
C:\>java Test
ABBCAD
C:\>java Test
ACADCB
C:\>java Test
ACBCBAD
C:\>java Test
ABBCAD
C:\>java Test
ACBCBAD
C:\>java Test
ACBCBAD
C:\>java Test
ABBCAD

27.
What will be the output of the program?
String s = "hello"; 
Object o = s; 
if( o.equals(s) )
{
    System.out.println("A"); 
} 
else
{
    System.out.println("B"); 
} 
if( s.equals(o) )
{
    System.out.println("C"); 
} 
else
{ 
    System.out.println("D"); 
}
  1. A
  2. B
  3. C
  4. D
1 and 3
2 and 4
3 and 4
1 and 2
Answer: Option
Explanation:
No answer description is available. Let's discuss.

28.
What will be the output of the program (in jdk1.6 or above)?
public class BoolTest 
{
    public static void main(String [] args) 
    {
        Boolean b1 = new Boolean("false");
        boolean b2;
        b2 = b1.booleanValue();
        if (!b2) 
        {
            b2 = true;
            System.out.print("x ");
        }
        if (b1 & b2) /* Line 13 */
        {
            System.out.print("y ");
        }
        System.out.println("z");
    }
}
z
x z
y z
Compilation fails.
Answer: Option
Explanation:
No answer description is available. Let's discuss.