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# 04-arrayintlist - CSE 143 Lecture 4 Implementing...

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Unformatted text preview: CSE 143 Lecture 4 Implementing ArrayIntList reading: 15.1 - 15.3 slides created by Marty Stepp http://www.cs.washington.edu/143/ 2 Exercise • Pretend for a moment that there is no ArrayList class . – Write a program that reads a file data.txt (of unknown size) full of integers and prints them in reverse order. 17 932085-32053278 100 3 – Output: 3 100-32053278 932085 17 3 "Unfilled array" solution • We are using an array to store a l i s t of values. – Only the values at indexes [0, s i z e - 1] are relevant. int nums = new int[100]; // make a big array int size = 0; Scanner input = new Scanner(new File("data.txt")); while (input.hasNextInt()) { nums[size] = input.nextInt(); // read each number size++; // into the array } for (int i = size - 1; i >= 0; i--) { System.out.println( nums[i] ); // print reversed } 5 s i z e i n d e x 1 2 3 4 5 6 . . . 9 8 9 9 v a l u e 17 932085 -32053278 100 3 ... 4 Possible list operations public static void add( int list, int size , int value, int index ) public static void remove( int list, int size , int index) public static void find( int list, int size , int value) public static void print( int list, int size ) ... • We could write methods that accept a l i s t array and its s i z e . – But since this data and this behavior are so closely related, it makes more sense to put them together into an object. – A list object can store an array of elements and a size. • It can also have methods for manipulating the list of elements. • This will give us abstraction (hide the details of how the list works) 5 Exercise • Let's write a class that implements a list using an int – We'll call it ArrayIntList – its behavior: •add( value ) , add( index , value ), •get( index ) , set( index , value ), •size(), isEmpty(), •remove( index ), •indexOf( value ), contains( value ), •toString(), ......
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04-arrayintlist - CSE 143 Lecture 4 Implementing...

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