Introduction to Java

1. Introduction to Java ArrayLists

2. Write a program that reads 3 integers and displays them for (inti = 0; i < 3; i=i+1) { intval = in.nextInt(); System.out.println(val); }

3. Write a program that reads integers contained in a file and display them in reverse order • Input: 5 2 76 8 1 • Output: 1 8 76 2 5 • Observations: • Can not start displaying until we have read the last value • The last value must be displayed first • Can not forget any values

4. int v1, v2, … vn v1= in.nextInt(); v2= in.nextInt(); … vn=in.nextInt(); System.out.println(vn); system.out.println(vn-1); … system.out.println(v1); • Write a program that reads integers contained in a file and display them in reverse order • Will not work!! • Don’t know how many variables do we need

5. ArrayList • A sequence of 0 or more values under a common name • Values of common types • Values are distinguished by their position a 1 5 3 2 18 11 0 1 2 3 4 5

6. Operations • create new ArrayList<Type>(); Creates an ArrayList of type Type with size 0; ArrayList <Integer> a = new ArrayList<Integer>();

7. Operations • add (x) • Increase the size of the ArrayList by 1 • Place value x at the end of ArrayList

8. Operations • int size() • return the size of the ArrayList

9. Operations • get (i) • return the value at position i of the ArrayList • i < size();

10. Operations • set(i, x) • sets the value at position i of the ArrayList to x • i < size();

11. Write a program that reads integers contained in a file and display them in reverse order • Input: 5 2 76 8 1 • Output: 1 8 76 2 5

12. Write a program that reads integers contained in a file and display them in Ascending order • Input: 5 2 76 8 1 • Output: 1 2 5 8 76