Which two can be used to create a new Thread?

1. Extend java.lang.Thread and override the run() method.
2. Extend java.lang.Runnable and override the start() method.
3. Implement java.lang.Thread and implement the run() method.
4. Implement java.lang.Runnable and implement the run() method.
5. Implement java.lang.Thread and implement the start() method.

void start() {  
    A a = new A(); 
    B b = new B(); 
    a.s(b);  
    b = null; /* Line 5 */
    a = null;  /* Line 6 */
    System.out.println("start completed"); /* Line 7 */
} 

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(); 
    } 
}

import java.io.*;
public class MyProgram 
{
    public static void main(String args[])
    {
        FileOutputStream out = null;
        try 
        {
            out = new FileOutputStream("test.txt");
            out.write(122);
        }
        catch(IOException io) 
        {
            System.out.println("IO Error.");
        }
        finally 
        {
            out.close();
        }
    }
}

public class Test 
{
    public static void main(String [] args) 
    {
        int I = 1;
        do while ( I < 1 )
        System.out.print("I is " + I);
        while ( I > 1 ) ;
    }
}

class MyThread extends Thread 
{
    public static void main(String [] args) 
    {
        MyThread t = new MyThread();
        Thread x = new Thread(t);
        x.start(); /* Line 7 */
    }
    public void run() 
    {
        for(int i = 0; i < 3; ++i) 
        {
            System.out.print(i + "..");
        }
    }
}

1. protected abstract void m1();
2. static final void m1(){}
3. synchronized public final void m1() {}
4. private native void m1();

1. f1 == f2
2. f1 == f3
3. f2 == f1[1]
4. x == f1[0]
5. f == f1[0]

import java.awt.Button;
class CompareReference 
{
    public static void main(String [] args) 
    {
        float f = 42.0f;
        float [] f1 = new float[2];
        float [] f2 = new float[2];
        float [] f3 = f1;
        long x = 42;
        f1[0] = 42.0f;
    }
}