public class DoubleArrayBag implements Cloneable {

// Invariant of the DoubleArrayBag class:

// 1. The number of elements in the bag is in the instance variable

// used, which is no more than data.length.

// 2. For an empty bag, we do not care what is stored in any of data;

// for a non-empty bag, the elements in the bag are stored in data[0]

// through data[used-1], and we don't care what's in the

// rest of data.

public static final int MAX_CAPACITY = 4000;

private double[ ] data;

private int used;

/**

* Initialize an empty bag * @post.

* This bag is empty and has a capacity of MAX_CAPACITY.

* @exception OutOfMemoryError

* Indicates insufficient memory for allocating the array

**/

public DoubleArrayBag( ) {

used = 0;

data = new double[MAX_CAPACITY];

}

/**

* Initialize a new bag as an exact copy of source

* @param source

* reference to bag that is to be copied

* @exception NullPointerException

* occurs when source is null

* @post.

* This bag is a copy of source and has a capacity of

* MAX_CAPACITY

**/

public DoubleArrayBag( DoubleArrayBag source ) {

if ( source == null ) {

throw new NullPointerException("source must not be null");

}

//Update this.used and copy over only the used data from source

//into this.data

// STUDENT IMPLEMENTATION OF ABOVE HERE-- consider use of System.arraycopy shown // in text }

/**

* Generate a copy of this bag. * @post. * x.clone() != x * x.clone().getClass() == x.getClass() * x.clone().equals( x ) * * @return * The return value is a copy of this bag. Subsequent changes to the * copy will not affect the original, nor vice versa. * **/ public DoubleArrayBag clone( ) { // Clone an DoubleArrayBag object. DoubleArrayBag answer; try { answer = (DoubleArrayBag) super.clone( ); answer.data = data.clone( ); return answer; } catch (CloneNotSupportedException e) { // This exception should not occur. But if it does, it would probably // indicate a programming error that made super.clone unavailable. // The most common error would be forgetting the "Implements Cloneable" // clause at the start of this class. throw new RuntimeException ("This class does not implement Cloneable"); } } /** * Compare this DoubleArrayBag to another object for equality of value * @param other * reference to another DoubleArrayBag * * @post. * x.equals(x) is true * if x.equals(y) then y.equals(x) * x.equals(null) is false * * @return * true if number of elements in this and other are the same AND if * the values of all the elements in the bag are the same and in the * same position in the bag * * @note. * If the value of other is null, then the return is false **/ @Override public boolean equals(Object other) { if ( other == null ) return false; boolean isEqual = false; if ( other instanceof DoubleArrayBag ) { DoubleArrayBag candidate = (DoubleArrayBag) other; //are we comparing this with this if (this == other) return true; if ( candidate.used != this.used ) return false; int index = 0; isEqual = true; // Inspect data from data[0] through data[used-1] at most // and compare with respective elements of candidate.data // to determine if all are ==. If a pair are not ==, then // set isEqual to false -- which terminates the loop // STUDENT IMPLEMENTATION OF ABOVE HERE } return isEqual; }