How to set class path in Eclipse?

[AmandaChenCa]

How to run a file which include a main type in Eclipse?each I try to run the following code , Eclipse always says the Selection does not contain a main type?
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import FSMApi.*;
import FSMIsEven.*;

public class Main_FSMIsEven
{

public Main_FSMIsEven()
{
}

public static void main(String[] args)
{
FSM fsm = new FSM( new FSMIsEven() );

try
{
fsm.Initialize();
fsm.Process( IDEvents.EVENT_input0 );
fsm.Process( IDEvents.EVENT_input1 );
fsm.Process( IDEvents.EVENT_input0 );
fsm.Process( IDEvents.EVENT_input1 );
fsm.Process( IDEvents.EVENT_input0 );
fsm.Process( IDEvents.EVENT_input1 );
if( fsm.IsFinal() )
{
System.out.println( "Final" );
}
else
{
System.out.println( "NonFinal" );
}
fsm.Finalize();
}
catch( FSMException e )
{
System.out.println( e );
}
}

public static void Func0()
{
System.out.println( "In Func0" );
}

public static void Func1()
{
System.out.println( "In Func1" );
}

public static void Func2()
{
System.out.println( "In Func2" );
}

public static void Func3()
{
System.out.println( "In Func3" );
}

}