ListArrayBased.java (3190B)
1 package lab2; 2 3 // ******************************************************** 4 // Array-based implementation of the ADT list. 5 // ********************************************************* 6 public class ListArrayBased implements ListInterface 7 { 8 9 private static final int MAX_LIST = 3; 10 protected Object []items; // an array of list items 11 protected int numItems; // number of items in list 12 13 public ListArrayBased() 14 { 15 items = new Object[MAX_LIST]; 16 numItems = 0; 17 } // end default constructor 18 19 public boolean isEmpty() 20 { 21 return (numItems == 0); 22 } // end isEmpty 23 24 public int size() 25 { 26 return numItems; 27 } // end size 28 29 public void removeAll() 30 { 31 // Creates a new array; marks old array for 32 // garbage collection. 33 items = new Object[MAX_LIST]; 34 numItems = 0; 35 } // end removeAll 36 37 public void add(int index, Object item) 38 throws ListIndexOutOfBoundsException 39 { 40 if (numItems == items.length ) //fixes implementation errors and programming errors. 41 { 42 throw new ListException("ListException on add"); 43 } // end if 44 if (index >= 0 && index <= numItems) 45 { 46 // make room for new element by shifting all items at 47 // positions >= index toward the end of the 48 // list (no shift if index == numItems+1) 49 for (int pos = numItems-1; pos >= index; pos--) //textbook code modified to eliminate logic error causing ArrayIndexOutOfBoundsException 50 { 51 items[pos+1] = items[pos]; 52 } // end for 53 // insert new item 54 items[index] = item; 55 numItems++; 56 } 57 else 58 { 59 // index out of range 60 throw new ListIndexOutOfBoundsException( 61 "ListIndexOutOfBoundsException on add"); 62 } // end if 63 } //end add 64 65 public Object get(int index) 66 throws ListIndexOutOfBoundsException 67 { 68 if (index >= 0 && index < numItems) 69 { 70 return items[index]; 71 } 72 else 73 { 74 // index out of range 75 throw new ListIndexOutOfBoundsException( 76 "ListIndexOutOfBoundsException on get"); 77 } // end if 78 } // end get 79 80 public void remove(int index) 81 throws ListIndexOutOfBoundsException 82 { 83 if (index >= 0 && index < numItems) 84 { 85 // delete item by shifting all items at 86 // positions > index toward the beginning of the list 87 // (no shift if index == size) 88 for (int pos = index+1; pos < numItems; pos++) //textbook code modified to eliminate logic error causing ArrayIndexOutOfBoundsException 89 90 { 91 items[pos-1] = items[pos]; 92 } // end for 93 items[numItems - 1] = null; // Fixes memory leak. 94 numItems--; 95 } 96 else 97 { 98 // index out of range 99 throw new ListIndexOutOfBoundsException( 100 "ListIndexOutOfBoundsException on remove"); 101 } // end if 102 } //end remove 103 104 105 106 }