Test03

Test 03 - Solution

Name : ______________________________________________________

When answering the following questions be sure to read all introductions - they may include important declarations or information needed to solve the questions.

You should be able to answer all 27 questions (in 3 groups) in less then 30 mins.

Group 1
Check whether the following loops are valid.
If they are valid you should also write down the output produced by the loop when it is executed.

Assume that the following declaration has been made: int j = 0;

Loop	Valid	Not valid	Output
for (int i = 0, i < 5, i++) System.out.print(i + ” ”);		X (commas used instead of semicolons)
for (i = 0; i < 5; i++) System.out.print(i + ” ”);		X (type of i not declared)
for (int i = 0; i <= 5; i++) System.out.print(i + ” ”);	X		0 1 2 3 4 5
for (int i = 0; i < 5; i++); System.out.print(i + ” ”);		X (as the body of the loop is empty (semicolon after loop-head) and i is not declared outside loop the print() will crash)
for (int i = 0; i < 5; i = i + 2) System.out.print(i + ” ”);	X		0 2 4
while (j <= 5) System.out.print(j + ” ”);	X		0 0 0 0 (infinite as j never changes)
while (j < 5){ System.out.print(j + ” ”); j++; }	X		0 1 2 3 4
while (j < 5) System.out.print( (j++) + ” ”);	X		0 1 2 3 4

Group 2
Assume that the following two classes are fully implemented:

Also assume the following declaration have been made: Person pers = new Person("Peter", "HighStreet 12", "Roskilde");

Which of the following statements are valid?

Statement	Valid	Not valid
pers.toString();	X
Person.toString();		X (toString() not static)
pers.getName();	X
String s = pers.getAddress();		X (getAddress() does not return String)
String s = Person.getAddress();		X (getAddress() not static)
Address a = pers.getAddress();	X
Address a = Person.getAddress();		X (getAddress() not static)
String city = Person.getAddress.getCity();		X (getAddress is a method(and is not static))
String city = (Address) pers.getCity();		X (getCity() not in Person)
String city = pers.getAddress().getCity();	X
String city = pers.getAddress.getCity();		X (getAddress() is a method)

Group 3
Which of the following implementations of the toString() method for the class Person would be valid?

toString()	Valid	Not valid
public String toString(){ String s = name + "\n" + street + "\n" + city; }		X (no return statement)
public String toString(){ return name + "\n" + street + "\n" + city; }		X (street and city not available in Person)
public String toString(){ return "Name" + name + "\n" + address; }	X
public String toString(){ return "Name" + name + "\n" + super.toString(); }	X
public String toString(){ return name + "\n" + address.getStreet() + address.getCity().; }		X (. before semicolon not correct)
public String toString(){ return "Name" + name + "\n" + address.street + address.city; }		X (street and city not public)
public String toString(){ return super.toString() + address; }	X
public String toString(){ return "Name" + name + "\nStreet" + address.getStreet() + "\nCity" + address.getCity(); }	X