1. Advanced Programming TA Session 2
Advanced Programing TA Session, Sharif University of Technology
TA Session 2

2. What are the properties of an Object?
State
Behavior
Identity
Book.java
class Book {
String title;
void printTitle() {
System.out.println("I am: " + title); }
Advanced Programing TA Session, Sharif University of Technology

3. Identity What is the output? class Book { String title;
void printTitle() {
System.out.println("I am: " + title); }
public static void main(String[] args) {
Book book1 = new Book(), book2 = new Book();
book1.title = "TIJ";
book2.title = "TIJ";
if (book1 == book2) {
System.out.println("equal");
Advanced Programing TA Session, Sharif University of Technology

4. Setting values in Arrays
Write a function to get a int[][] array and a number as input and set all cells of the array to that number.
class TwoDimArrayUtil {
public static void setArray(int[][] array, int value) { }
public static void main(String[] args) {
int [][] A;
A = new int[3][];
A[0] = new int[2];
A[1] = new int[4];
A[2] = new int[1];
Advanced Programing TA Session, Sharif University of Technology

5. Setting values in Arrays - Solution
Write a function to get a int[][] array and a number as input and set all cells of the array to that number.
class TwoDimArrayUtil {
public static void setArray(int[][] array, int value) {
for (int i = 0; i < array.length; i++) {
for (int j = 0; j < array[i].length; j++) {
array[i][j] = value; }
public static void main(String[] args) {
int [][] A;
A = new int[3][];
A[0] = new int[2];
A[1] = new int[4];
A[2] = new int[1];
Advanced Programing TA Session, Sharif University of Technology

6. Getting values in arrays
Write a function to convert an int[][] array to a String, like this:
[[1, 2], [3, 4, 5], [6, 7]]
class TwoDimArrayUtil {
public static String convertArrayToString(int[][] array) { }
public static void main(String[] args) {
int [][] A;
A = new int[3][];
A[0] = new int[] {1, 2};
A[1] = new int[] {3, 4, 5};
A[2] = new int[] {6, 7};
System.out.println(convertArrayToString(A));
Advanced Programing TA Session, Sharif University of Technology

7. Getting values in arrays - Solution
public static String convertArrayToString(int[][] array) {
String val = "[";
for (int i = 0; i < array.length; i++) {
if (i != 0) val += ", ";
val += "[";
for (int j = 0; j < array[i].length; j++) {
if (j != 0) val += ", ";
val += array[i][j]; }
val += "]";
return val;
Advanced Programing TA Session, Sharif University of Technology

8. Changing arrays What is the output?
class TwoDimArrayUtil {
static void changeSize(int[][] A, int r, int s) {
A[r] = new int[s]; }
public static void main(String[] args) {
int [][] A;
A = new int[3][];
A[0] = new int[] {1, 2};
A[1] = new int[] {3, 4, 5};
A[2] = new int[] {6, 7};
changeSize(A, 0, 10);
System.out.println(A[0].length);
Advanced Programing TA Session, Sharif University of Technology
The output is 10, because arrays are passed by reference.

9. Swap int What is the output?
class Swap1 {
static void swap(int x, int y) {
int t = x;
x = y;
y = t; }
public static void main(String[] args) {
int x = 10, y = 20;
swap(x, y);
System.out.println(x + ", " + y);
Advanced Programing TA Session, Sharif University of Technology
The output is “10, 20” because primitive data types are passed by reference.

10. Swap Integer What is the output?
class Swap2 {
static void swap(Integer x, Integer y) {
Integer t = x;
x = y;
y = t; }
public static void main(String[] args) {
Integer x = 10, y = 20;
swap(x, y);
System.out.println(x + ", " + y);
Advanced Programing TA Session, Sharif University of Technology
Still, The output is “10, 20”, but for another reason: Because we are modifying the reference, not the content

11. Correct Swapper
Advanced Programing TA Session, Sharif University of Technology