public class DoubleArraySeq implements Cloneable
{
// Invariant of the DoubleArraySeq class:
// 1. The number of elements in the seqeunces is in the instance variable
// manyItems.
// 2. For an empty sequence (with no elements), we do not care what is
// stored in any of data; for a non-empty sequence, the elements of the
// sequence are stored in data[0] through data[manyItems-1], and we
// don't care what's in the rest of data.
// 3. If there is a current element, then it lies in data[currentIndex];
// if there is no current element, then currentIndex equals manyItems.
private double[] data;
private int manyItems;
private int currentIndex;
/**
* Initialize an empty sequence with an initial capacity of 10. Note that
* the addAfter and addBefore methods work efficiently (without needing more
* memory) until this capacity is reached.
* @param - none
* @postcondition
* This sequence is empty and has an initial capacity of 10.
* @exception OutOfMemoryError
* Indicates insufficient memory for:
* new double[10].
**/
public DoubleArraySeq( )
{
final int INITIAL_CAPACITY = 10;
data = new double[INITIAL_CAPACITY];
manyItems = 0;
currentIndex = 0;
}
/**
* Initialize an empty sequence with a specified initial capacity. Note that
* the addAfter and addBefore methods work efficiently (without needing more
* memory) until this capacity is reached.
* @param initialCapacity
* the initial capacity of this sequence
* @precondition
* initialCapacity is non-negative.
* @postcondition
* This sequence is empty and has the given initial capacity.
* @exception IllegalArgumentException
* Indicates that initialCapacity is negative.
* @exception OutOfMemoryError
* Indicates insufficient memory for:
* new double[initialCapacity].
**/
public DoubleArraySeq(int initialCapacity)
{
if (initialCapacity < 0)
{
throw new IllegalArgumentException("The initialCapacity is negative: " +initialCapacity);
}
data = new double[initialCapacity];
manyItems = data.length;
currentIndex = 0;
}
/**
* Add a new element to this sequence, after the current element.
* If the new element would take this sequence beyond its current capacity,
* then the capacity is increased before adding the new element.
* @param element
* the new element that is being added
* @postcondition
* A new copy of the element has been added to this sequence. If there was
* a current element, then the new element is placed after the current
* element. If there was no current element, then the new element is placed
* at the end of the sequence. In all cases, the new element becomes the
* new current element of this sequence.
* @exception OutOfMemoryError
* Indicates insufficient memory for increasing the sequence's capacity.
* @note
* An attempt to increase the capacity beyond Integer.MAX_VALUE will cause
* the sequence to fail with an arithmetic overflow.
**/
public void addAfter(double element)
{
if (manyItems == data.length)
{//try to double capacity
ensureCapacity(manyItems*2 + 1);
}
if (!isCurrent())
{
currentIndex = manyItems;
}
for (int i = manyItems; i > currentIndex+1; i--)
{
data[i] = data[i-1];
}
data[currentIndex+1] = element;
manyItems++;
currentIndex++;
}
/**
* Add a new element to this sequence, before the current element.
* If the new element would take this sequence beyond its current capacity,
* then the capacity is increased before adding the new element.
* @param element
* the new element that is being added
* @postcondition
* A new copy of the element has been added to this sequence. If there was
* a current element, then the new element is placed before the current
* element. If there was no current element, then the new element is placed
* at the start of the sequence. In all cases, the new element becomes the
* new current element of this sequence.
* @exception OutOfMemoryError
* Indicates insufficient memory for increasing the sequence's capacity.
* @note
* An attempt to increase the capacity beyond Integer.MAX_VALUE will
* cause the sequence to fail with an arithmetic overflow.
**/
public void addBefore(double element)
{
if (manyItems == data.length)
{//try to double capacity
ensureCapacity(manyItems*2 + 1);
}
if (!isCurrent())
currentIndex = 0;
for (int i = manyItems; i > currentIndex; i--)
{
data[i] = data[i-1];
}
data[currentIndex] = element;
manyItems++;
}
/**
* Place the contents of another sequence at the end of this sequence.
* @param addend
* a sequence whose contents will be placed at the end of this sequence
* @precondition
* The parameter, addend, is not null.
* @postcondition
* The elements from addend have been placed at the end of
* this sequence. The current element of this sequence remains where it
* was, and the addend is also unchanged.
* @exception NullPointerException
* Indicates that addend is null.
* @exception OutOfMemoryError
* Indicates insufficient memory to increase the size of this sequence.
* @note
* An attempt to increase the capacity beyond
* Integer.MAX_VALUE will cause an arithmetic overflow
* that will cause the sequence to fail.
**/
public void addAll(DoubleArraySeq addend)
{
if (addend == null)
throw new NullPointerException("addend is null");
ensureCapacity(manyItems + addend.manyItems);
System.arraycopy(addend.data, 0, data, manyItems, addend.manyItems);
manyItems = manyItems + addend.manyItems;
}
/**
* Move forward, so that the current element is now the next element in
* this sequence.
* @param - none
* @precondition
* isCurrent() returns true.
* @postcondition
* If the current element was already the end element of this sequence
* (with nothing after it), then there is no longer any current element.
* Otherwise, the new element is the element immediately after the
* original current element.
* @exception IllegalStateException
* Indicates that there is no current element, so
* advance may not be called.
**/
public void advance( )
{
if (!isCurrent() || currentIndex >= manyItems -2)
{
throw new IllegalStateException ("Current Index is at the End of Array");
}
else
{
currentIndex++;
}
}
/**
* Generate a copy of this sequence.
* @param - none
* @return
* The return value is a copy of this sequence. Subsequent changes to the
* copy will not affect the original, nor vice versa.
* @exception OutOfMemoryError
* Indicates insufficient memory for creating the clone.
**/
public DoubleArraySeq clone( )
{
// Clone a DoubleArraySeq object.
DoubleArraySeq answer;
try
{
answer = (DoubleArraySeq) super.clone( );
}
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");
}
answer.data = (double [ ]) data.clone( );
return answer;
}
/**
* Create a new sequence that contains all the elements from one sequence
* followed by another.
* @param s1
* the first of two sequences
* @param s2
* the second of two sequences
* @precondition
* Neither s1 nor s2 is null.
* @return
* a new sequence that has the elements of s1 followed by the
* elements of s2 (with no current element)
* @exception NullPointerException.
* Indicates that one of the arguments is null.
* @exception OutOfMemoryError
* Indicates insufficient memory for the new sequence.
* @note
* An attempt to create a sequence with a capacity beyond
* Integer.MAX_VALUE will cause an arithmetic overflow
* that will cause the sequence to fail.
**/
public static DoubleArraySeq concatenation(DoubleArraySeq s1, DoubleArraySeq s2)
{
if ((s1 == null)&& (s2 == null))
throw new NullPointerException("s1 or s2 is null");
DoubleArraySeq s3 = new DoubleArraySeq();
// s3.data[]= s1.data[] + s2.data[];
s3.manyItems = s1.manyItems + s2.manyItems;
s3.currentIndex = s1.currentIndex + s2.currentIndex;
return s3;
}
/**
* Change the current capacity of this sequence.
* @param minimumCapacity
* the new capacity for this sequence
* @postcondition
* This sequence's capacity has been changed to at least minimumCapacity.
* If the capacity was already at or greater than minimumCapacity,
* then the capacity is left unchanged.
* @exception OutOfMemoryError
* Indicates insufficient memory for: new int[minimumCapacity].
**/
public void ensureCapacity(int minimumCapacity)
{
double[] biggerArray;
if (data.length < minimumCapacity)
{
biggerArray = new double [minimumCapacity];
System.arraycopy(data, 0, biggerArray, 0, manyItems);
data = biggerArray;
}
}
/**
* Accessor method to get the current capacity of this sequence.
* The add method works efficiently (without needing
* more memory) until this capacity is reached.
* @param - none
* @return
* the current capacity of this sequence
**/
public int getCapacity( )
{
return data.length;
}
/**
* Accessor method to get the current element of this sequence.
* @param - none
* @precondition
* isCurrent() returns true.
* @return
* the current element of this sequence
* @exception IllegalStateException
* Indicates that there is no current element, so
* getCurrent may not be called.
**/
public double getCurrent( )
{
if (isCurrent())
{
return currentIndex;
}
else
{
throw new IllegalStateException("No Current Element");
}
}
/**
* Accessor method to determine whether this sequence has a specified
* current element that can be retrieved with the
* getCurrent method.
* @param - none
* @return
* true (there is a current element)
* or false (there is no current element at the moment)
**/
public boolean isCurrent( )
{
if (currentIndex > 0)
{
return true;
}
else
{
return false;
}
}
/**
* Remove the current element from this sequence.
* @param - none
* @precondition
* isCurrent() returns true.
* @postcondition
* The current element has been removed from this sequence, and the
* following element (if there is one) is now the new current element.
* If there was no following element, then there is now no current
* element.
* @exception IllegalStateException
* Indicates that there is no current element, so
* removeCurrent may not be called.
**/
public void removeCurrent( )
{
if (isCurrent() == true)
{
if (currentIndex == manyItems - 1)
{
//On last item, no elements to move and decrementing manyItems below will eliminate this element,
// do nothing
}
else
{
//Shuffle elements over
for (int i = currentIndex; i <manyItems - 1; i++)
{
data[i] = data[i+1];
}
}
manyItems--;
}
else
{
throw new IllegalStateException
("There is no current element to remove!");
}
}
/**
* Determine the number of elements in this sequence.
* @param - none
* @return
* the number of elements in this sequence
**/
public int size( )
{
return manyItems;
}
/**
* Set the current element at the front of this sequence.
* @param - none
* @postcondition
* The front element of this sequence is now the current element (but
* if this sequence has no elements at all, then there is no current
* element).
**/
public void start( )
{
if(this==null)
throw new NullPointerException
("Current Index is 0");
else
currentIndex = 0;
}
/**
* Reduce the current capacity of this sequence to its actual size (i.e., the
* number of elements it contains). The current item does not change.
* @param - none
* @postcondition
* This sequence's capacity has been changed to its current size.
* @exception OutOfMemoryError
* Indicates insufficient memory for altering the capacity.
**/
public void trimToSize( )
{
double[] trimmedArray;
if (data.length != manyItems)
{
trimmedArray = new double [manyItems];
System.arraycopy(data, 0, trimmedArray, 0, manyItems);
data = trimmedArray;
}
}
/**
* Provide a string representation of the sequence with current item
* in parentheses
* @param - none
* @postcondition string representation returned but sequence is unchanged
* @return string displaying sequence
**/
public String toString( )
{
String answer = "";
for (int i = 0; i < manyItems; i++) {
if (i == currentIndex) {
answer += "(" + data[i] + ") ";
} else {
answer += data[i] + " ";
}
}
return answer;
}
}
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