Question

Write these java classes:

1) DynArray.java: a class that models some of the functionality of the Java ArrayList. This class is not complete and must be modified as such:

Write the method body for the default constructor

Write the method body for the methods: arraySize(), elements(), grow(), shrink(). The incomplete code is provided here:

public class DynArray
{
private double[] array;
private int size;
private int nextIndex;
  
public int arraySize()
{

}
  
public int elements()
{

}

public DynArray()
{

}
  
private void grow()
{

}
  
private void shrink()
{

}
}

2) DynArrayDriver.java A simple driver class to test your DynArray class, you must write this class from scratch.

Thanks.

Answer 1

//Create java class DynArray.java

public class DynArray {

public double array[];
private int size;
private int nextIndex;

//constructor to initialise the variabls
public DynArray() {
array = new double[1];
nextIndex = 0;//next index is 0
size = 1;// size of the array initially 1
}

public int arraySize() {
//return size of array
return size;
}

public int elements() {
//return element count
return nextIndex;
}
//makes size double of array

private void grow() {
double temp[] = null;
if (nextIndex == size) {
temp = new double[2 * size];//temp array is double in size
for (int i = 0; i < size; i++) {
temp[i] = array[i];//copy all elements in temp array
}
}
array = temp;
size = size * 2;
}

public void shrink() {
double temp[] = null;
if (nextIndex > 0) {

// temp is a count size array
// and store array elements
temp = new double[nextIndex];
for (int i = 0; i < nextIndex; i++) {

// copy all array value into temp
temp[i] = array[i];
}

size = nextIndex;

// count size array temp initialize
// into variable array again
array = temp;
}
}

//we need to add method to add new element in array
public void add(double data) {
// check no of element is equql to size of array
if (nextIndex == size) {
grow(); // make array size double
} // insert element at end of array
array[nextIndex] = data;
nextIndex++;
}
}
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//Craete driver class DynArrayDriver.java

public class DynArrayDriver {

//driver class for DynArray.java
public static void main(String[] args) {
//create object of DynArray class
DynArray dyn = new DynArray();
System.out.println("Size of DynArray " + dyn.arraySize());//check size of array using arraySIze function
System.out.println("Total elements in DynArray " + dyn.elements());//get element count using elements()
dyn.add(10);//add element to the array
  
dyn.add(25);
System.out.println("Size of DynArray "+dyn.arraySize());
dyn.add(60);
dyn.add(1.5);
System.out.println("Total Elements in Array "+dyn.elements());
System.out.println("Elements of DynArray");
for(int i=0;i<dyn.elements();i++)
{
System.out.print(dyn.array[i]+" ");//here array needs to public to access it in another class
}
System.out.println("");
}
}

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