Lab 2

Prepare: 1.Create a folder named lab2 inside the workspace. 2.Download RecordDB.java and Record.java from the lab document. 3.Change the file name RecordDB.java to DynamicRecordDB.java. 4.Launch Eclipse and create a new project named lab2. 5.Open DynamicRecordDB.java. 6. Subtitute "RecordDB" in DynamicRecordDB.java by "DynamicRecordDB" everywhere.

1. Change the type of maxRecords from static int to int. Change the default value of maxRecords from 200 to Change the declaration of recordList. private static int maxRecords = 200; private int numRecords = 0; private Record recordList[] = new Record[maxRecords]; private int maxRecords = 1; private int numRecords = 0; private Record recordList[];

3. Add two constructors: DynamicRecordDB() and DynamicRecordDB( int n ). // The default constructor; allocates an array of size 1. DynamicRecordDB( ) { recordList = new Record[ maxRecords ]; } // Allocates an array of size n. // If the user knows the maximum size of the employee // database, they might prefer to use this constructor DynamicRecordDB( int n ) { //update maxRecords to n maxRecords = n; //Create an array of size=maxRecords. recordList = new Record[ maxRecords ]; }

4. Modify insert method to double the size of recordList when overflow may occur. public void insert ( Record rec ) { // Check for overflow if ( numRecords == maxRecords – 1 ) { return;// Increase the size of the array maybe } …… Do nothing and return if overflow may occur. old version

public void insert (Record rec) { // Double the size of the array, if overflow may occur. if (numRecords == maxRecords-1) { //create of a new array of the double size Record[ ] tempRecord = new Record[ 2 * maxRecords ]; // Copy the contents of recordList to tempRecord for( int i = 0; i < maxRecords; i++) tempRecord[ i ] = recordList[ i ]; // Make recordList point to tempRecord recordList = tempRecord; //Change maxRecords to the new value maxRecords = 2 * maxRecords; //return; } ……

Time of insertion operations

Average time of each insertion operation