//5.14  null as arg for ctor
class sample
{
    sample(String s)
    {
	System.out.println("String");
    }
    sample(Object o)
    {
	System.out.println("Object");
    }
    //will be ambiguous syntax error:
    //    sample(StringBuffer sb)
    //    {
    ///	System.out.println("StringBuffer");
    //    }
}
class constructor
{
    public static void main(String arg[])
    {
	//matches both STring and Object, does more specific, ie. String
	sample s1=new sample(null);     
	//	sample s2=new sample(12);  //no such ctor error
	//	sample s3=new sample();    //no such ctor error

    }
}
/*
//5.13  static methods bound at compile-time!
class Child extends Parent {
    public static int test (int i) {
	return 20;
    }
    public static void main(String [] args) {
	Parent c = new Child();
	System.out.println(c.test(10));
    }
}
class Parent {
    public static int test(int i) {
	return 5;
    }
}
*/

/*
//5.6

interface Observer {}
class ApBase implements Runnable {
    public void run(){}
}
class ApDerived extends ApBase implements Observer {}
class arf {
    public static void main(String[] args) {
	ApBase aBase = new ApBase();
	ApDerived aDer = new ApDerived();
	Runnable rn = aDer;
	//	Observer ob = aBase;  //syntax error
	//Observer ob2 = (Observer) aBase;  //compiles but runtime error
	//aDer = aBase;    //compile error: sub = super
	//ApDerived ad2 = (ApDerived) aBase;  //runtime error: sub = (sub)super
	aBase = aDer;   //super = sub
	aBase = (ApBase)aDer;    //redundant cast
	//because super ref has actual sub ref, can cast to sub:
	if (aBase instanceof ApDerived) {
	    System.out.println("actual super is instanceof sub now");
	    ApDerived ad2 = (ApDerived) aBase;
	}
	if (aDer instanceof ApBase) 
	    System.out.println("sub is always instanceof super");
    }
}
*/


/*
//5.3
class arf {
    static String s;
    public static void main(String[] args) {
	//int index = args[0].indexOf('a'); 
	//int index = args[0].indexOf("a"); 
	int index = args[0].indexOf("asdf"); 
	System.out.println(index);  //-1 if not found
	String tmp = args[0].substring(0,index);   //index cannot be -1
	//String tmp = args[0].substring(0,args[0].indexOf('a'));
	System.out.println(tmp);
    }
}
*/

/*
//4.3
class Char
{
    static int var;
    public static void main(String arg[])
    {
	while(var < 10)
	    {
		System.out.println("Hello");
	    }
	while(var < 10)
	    {
	    }
	do;
	while(false);
	do
	    {
		;
	    }
	while(false);
    }
}

*/

/*
//4.1
class exam41 {
    static String s;
    public static void main(String[] args) {
	System.out.println(s==null?"is null":"not null");
	amethod(s);
    }
    static void amethod(String s) throws NullPointerException {
	float factor;
	try {
	    //factor = Float.valueOf(args[0]).floatValue();
	    factor = Float.valueOf(s).floatValue();
	    System.out.println("worked");
	} catch (NullPointerException e) {
	    System.out.println(e.getMessage());
	    throw e;
	    //	    factor = Float.NaN;
	    //	} catch (NullPointerException e) {
	    // System.out.println("null pointer exception: "+e.getMessage());
	} finally {
	    System.out.println("in finally");
	}
	System.out.println("at end of main");
    }
}
*/

/*
//3.9
abstract class Ghost {
    //    void haunt();   //syntax error
    abstract void haunt();
    void haunt2() {}
}
*/

/*
//3.2
class arrayinits {
    public static void main(String[] args) {
	//int [][]a1 = {{1,2},{1},{},{1,2,3}};
	//int [][]a1 = new int[][]{{1,2},{1},{},{1,2,3}};
	int [][]a1 = {{1,2},new int[2]};
	//	int []a1 = new int [2]{1,2};   //syntax bad
	for (int i=0; i<a1.length; i++) {
	    for (int j=0; j<a1[i].length; j++) 
		System.out.print(a1[i][j]+" ");
	    System.out.println();
	}
    }
}
*/

/*
//2.10
class AA{}
class BB extends AA{}
class Q6 {
    public static void main(String[] args) {
	//AA a=null;
	//AA a= new AA();
	//BB b = (BB)a;  //runtime error if a is instantiated as AA
	BB b = new BB();
	AA a = b;
	//AA a = (BB)b;
	System.out.println(a);
	System.out.println(a instanceof BB);
	System.out.println(a instanceof AA);
	System.out.println(b);
	System.out.println(b instanceof BB);
	System.out.println(b instanceof AA);
    }
}
*/

/*
public class exam4_5 {
    public static void main(String[] args) {
	System.out.println("A");
	try {
	    return;
	} catch (Exception e) {
	    System.out.println("B");
	}
	System.out.println("C");
    }
}
*/
/*
public class exam2_6 {
    public static void main(String[] args) {
	exam2_6 o = new exam2_6();
	o.amethod();
    }



    public void amethod() {
	int i = 99;
	ValHold v = new ValHold();
	v.i = 30;
	another(v,i);
	System.out.println(v.i);
    }
    public void another(ValHold v, int i) {
	i = 0;
	v.i = 20;
	ValHold vh = new ValHold();
	v = vh;
	System.out.println(v.i+" "+i);
    }
}
class ValHold {
    public int i = 10;
}
*/