Something went wrong in the following program. What fix is needed to make

Thread$-$A and Thread$-$B run concurrently?

public class Main

$\{$

private static class ThreadDemo extends Thread

public ThreadDemo$($String name$)\{$

this.setName$($name$)$;

$\}$

@Override

public void run$()\{$

System.out.printIn$("$Running $"+$ this.getName$())$;

try $\{$

for$($int $i=20$; i$>0$; $i--$

System.out.printIn$("$Thread: $"+$ this.getName$()+","+$ i$)$;

Thread.sleep$(50)$;

$\}$

$\}$ catch $($InterruptedException e$)\{$

System.out.printIn$("$Thread $"+$ this.getName$()+"$ interrupted."$)$;

$\}$

System.out.printIn$("$Thread $"+$ this.getName$()+"$ exiting."$)$;

$\}$

$1$

$\}$

public static void main$($String args$[])$

$\{$

ThreadDemo T$1=$ new ThreadDemo$("$Thread$-$A$")$;

ThreadDemo T$2=$ new ThreadDemo$("$Thread$-$B$")$;

T$1.$run$()$;

T$2.$run$()$;

$\}$

$1$

In the main method, calls to join are needed.

run must be public.

ThreadDemo must be public.

In the main method, calls to run should be replaced with calls to start.

In the main method, calls to run should be replaced with calls to join.

ThreadDemo needs to declare a start method.

Nothing. They already run concurrently.

Select all true statements.

An abstract method ends in a semicolon.

Abstract classes can be instantiated.

An abstract method has a header, but no body.

Interfaces can be instantiated.

A Java class can implement multiple interfaces.