import java.util.ArrayList;

public class UsageExample {
	
	public static void main( String args[] ) {
		// example without generics
		ArrayList numList = new ArrayList();
		numList.add(new Integer(1));
		numList.add(new Integer(2));
		
		// no type checking, we can put strings into this list
		numList.add(new String("bad idea") ); 
		
		// can't do this: get returns an Object
//		Integer i1 = numList.get(0);
//		Integer i2 = numList.get(1);
		
		// need to cast the returned Object reference to Integer
		Integer i1 = (Integer) numList.get(0); 
		Integer i2 = (Integer) numList.get(1);
		
		// this line would cause the program to crash:
//		Integer i3 = (Integer) numList.get(2);
		
		System.out.println( i1.intValue() + i2.intValue() );
		
		// now, with generics:
		// between the < and > characters is the generic type parameter
		ArrayList<Integer> numListGeneric = new ArrayList<Integer>();
		
		numListGeneric.add(new Integer(1));
		numListGeneric.add(2);
//		numListGeneric.add(new String("bad idea"));  // this will not compile
		
		i1 = numListGeneric.get(0);	// no casting needed
		i2 = numListGeneric.get(1);
		
		System.out.println( i1.intValue() + i2.intValue() );
		
		
	}

}