При тестировании методов isEmpty и removeAll для метода Unsorted List с использованием JUnit все тесты приводят к исключениям пустых указателей.
Я попытался создать метод, расширяющий метод Unsorted List, и он работаетпри использовании нулевого теста, но впоследствии дает исключения нулевого указателя.С помощью теста метода removeAll все они дают исключение пустого указателя.
ArrayUnsortedList:
//----------------------------------------------------------------------------
// ArrayUnsortedList.java by Dale/Joyce/Weems Chapter 6
//
// Implements the ListInterface using an array.
//
// Null elements are not permitted on a list.
//
// Two constructors are provided: one that creates a list of a default
// original capacity, and one that allows the calling program to specify the
// original capacity.
//----------------------------------------------------------------------------
package lists;
public class ArrayUnsortedList<T> implements ListInterface<T>
{
protected final int DEFCAP = 100; // default capacity
protected int origCap; // original capacity
protected T[] list; // array to hold this list’s elements
protected int numElements = 0; // number of elements in this list
protected int currentPos; // current position for iteration
// set by find method
protected boolean found; // true if element found, otherwise false
protected int location; // indicates location of element if found
public ArrayUnsortedList()
{
list = (T[]) new Object[DEFCAP];
origCap = DEFCAP;
}
public ArrayUnsortedList(int origCap)
{
list = (T[]) new Object[origCap];
this.origCap = origCap;
}
protected void enlarge()
// Increments the capacity of the list by an amount
// equal to the original capacity.
{
// Create the larger array.
T[] larger = (T[]) new Object[list.length + origCap];
// Copy the contents from the smaller array into the larger array.
for (int i = 0; i < numElements; i++)
{
larger[i] = list[i];
}
// Reassign list reference.
list = larger;
}
protected void find(T target)
// Searches list for an occurence of an element e such that
// e.equals(target). If successful, sets instance variables
// found to true and location to the array index of e. If
// not successful, sets found to false.
{
location = 0;
found = false;
while (location < numElements)
{
if (list[location].equals(target))
{
found = true;
return;
}
else
location++;
}
}
public void add(T element)
// Adds element to this list.
{
if (numElements == list.length)
enlarge();
list[numElements] = element;
numElements++;
}
public boolean remove (T element)
// Removes an element e from this list such that e.equals(element)
// and returns true; if no such element exists, returns false.
{
find(element);
if (found)
{
list[location] = list[numElements - 1];
list[numElements - 1] = null;
numElements--;
}
return found;
}
public int size()
// Returns the number of elements on this list.
{
return numElements;
}
public boolean contains (T element)
// Returns true if this list contains an element e such that
// e.equals(element); otherwise, returns false.
{
find(element);
return found;
}
public T get(T element)
// Returns an element e from this list such that e.equals(element);
// if no such element exists, returns null.
{
find(element);
if (found)
return list[location];
else
return null;
}
public String toString()
// Returns a nicely formatted string that represents this list.
{
String listString = "List:\n";
for (int i = 0; i < numElements; i++)
listString = listString + " " + list[i] + "\n";
return listString;
}
public void reset()
// Initializes current position for an iteration through this list,
// to the first element on this list.
{
currentPos = 0;
}
public T getNext()
// Preconditions: The list is not empty
// The list has been reset
// The list has not been modified since the most recent reset
//
// Returns the element at the current position on this list.
// If the current position is the last element, it advances the value
// of the current position to the first element; otherwise, it advances
// the value of the current position to the next element.
{
T next = list[currentPos];
if (currentPos == (numElements - 1))
currentPos = 0;
else
currentPos++;
return next;
}
public boolean isEmpty() {
if(list == null || list.length == 0) {
return true;
}
else
return false;
}
public int removeAll(T element)
{
int count = 0;
find(element);
while (found)
{
find(element);
list[location] = list[numElements - 1];
list[numElements - 1] = null;
numElements--;
count ++;
}
return count;
}
}
Тесты:
isEmpty:
package testList;
import static org.junit.jupiter.api.Assertions.*;
import org.junit.Before;
import org.junit.jupiter.api.Test;
import ApplicationLevelMethods.Methods;
import lists.ArrayUnsortedList;
class Test_AppLevel_isEmpty {
ArrayUnsortedList<String> testNull, testOne, testMult;
@Before
public void setUp() {
testNull = new ArrayUnsortedList<String>();
testOne = new ArrayUnsortedList<String>();
testMult = new ArrayUnsortedList<String>();
}
@Test
public void test_null() {
assertTrue(testNull.isEmpty());
}
@Test
public void test_one() {
testOne.add("one");
assertFalse(testOne.isEmpty());
}
@Test
public void test_multiple() {
testMult.add("one");
testMult.add("two");
testMult.add("three");
assertFalse(testMult.isEmpty());
}
}
removeAll:
package testList;
import static org.junit.Assert.assertEquals;
import static org.junit.jupiter.api.Assertions.*;
import org.junit.Before;
import org.junit.jupiter.api.Test;
import lists.ArrayUnsortedList;
class Test_AppLevel_removeAll {
ArrayUnsortedList<String> testNull, testOne, testMult;
@Before
public void setUp() {
testNull = new ArrayUnsortedList<String>();
testOne = new ArrayUnsortedList<String>();
testMult = new ArrayUnsortedList<String>();
}
@Test
void test_Null() {
testNull.removeAll("one");
assertEquals(0,testNull.removeAll("one"));
}
@Test
void test_One() {
testOne.add("one");
assertEquals(1,testOne.removeAll("one"));
}
}