5
好吧，我有一個非常惱人的錯誤。它來自我的retainAll方法。問題是我最終輸出了1,3,5，但我需要1,3,5,7,9。以下是MySet和驅動程序類的代碼在我的「自定義設置」實施中需要幫助
public class MySetTester {
public static void main(String[]args) {
MySet<String> strings = new MySet<String>();
strings.add("Hey!");
strings.add("Hey!");
strings.add("Hey!");
strings.add("Hey!");
strings.add("Hey!");
strings.add("Listen!");
strings.add("Listen!");
strings.add("Sorry, I couldn't resist.");
strings.add("Sorry, I couldn't resist.");
strings.add("(you know you would if you could)");
System.out.println("Testing add:\n");
System.out.println("Your size: " + strings.size()
+ ", contains(Sorry): " + strings.contains("Sorry, I couldn't resist."));
System.out.println("Exp. size: 4, contains(Sorry): true\n");
MySet<String> moreStrings = new MySet<String>();
moreStrings.add("Sorry, I couldn't resist.");
moreStrings.add("(you know you would if you could)");
strings.removeAll(moreStrings);
System.out.println("Testing remove and removeAll:\n");
System.out.println("Your size: " + strings.size()
+ ", contains(Sorry): "
+ strings.contains("Sorry, I couldn't resist."));
System.out.println("Exp. size: 2, contains(Sorry): false\n");
MySet<Integer> ints = new MySet<Integer>();
for (int i = 0; i < 100; i++) {
ints.add(i);
}
System.out.println("Your size: " + ints.size());
System.out.println("Exp. size: 100\n");
for (int i = 0; i < 100; i += 2) {
ints.remove(i);
}
System.out.println("Your size: " + ints.size());
System.out.println("Exp. size: 50\n");
MySet<Integer> zeroThroughNine = new MySet<Integer>();
for (int i = 0; i < 10; i++) {
zeroThroughNine.add(i);
}
ints.retainAll(zeroThroughNine);
System.out.println("ints should now only retain odd numbers"
+ " 0 through 10\n");
System.out.println("Testing your iterator:\n");
for (Integer i : ints) {
System.out.println(i);
}
System.out.println("\nExpected: \n\n1 \n3 \n5 \n7 \n9\n");
System.out.println("Yours:");
for (String s : strings) {
System.out.println(s);
}
System.out.println("\nExpected: \nHey! \nListen!");
strings.clear();
System.out.println("\nClearing your set...\n");
System.out.println("Your set is empty: " + strings.isEmpty());
System.out.println("Exp. set is empty: true");
}
}
這裏是主代碼。但仍然閱讀最重要的部分，因爲這就是我的例子。
import java.util.Set;
import java.util.Collection;
import java.lang.Iterable;
import java.util.Iterator;
import java.util.Arrays;
import java.lang.reflect.Array;
public class MySet<E> implements Set<E>, Iterable<E>
{
// instance variables - replace the example below with your own
private E[] backingArray;
private int numElements;
/**
* Constructor for objects of class MySet
*/
public MySet()
{
backingArray=(E[]) new Object[5];
numElements=0;
}
public boolean add(E e){
for(Object elem:backingArray){
if (elem==null ? e==null : elem.equals(e)){
return false;
}
}
if(numElements==backingArray.length){
E[] newArray=Arrays.copyOf(backingArray,backingArray.length*2);
newArray[numElements]=e;
numElements=numElements+1;
backingArray=newArray;
return true;
}
else{
backingArray[numElements]=e;
numElements=numElements+1;
return true;
}
}
public boolean addAll(Collection<? extends E> c){
for(E elem:c){
this.add(elem);
}
return true;
}
public void clear(){
E[] newArray=(E[])new Object[backingArray.length];
numElements=0;
backingArray=newArray;
}
public boolean equals(Object o){
if(o instanceof Set &&(((Set)o).size()==numElements)){
for(E elem:(Set<E>)o){
if (this.contains(o)==false){
return false;
}
return true;
}
}
return false;
}
public boolean contains(Object o){
for(E backingElem:backingArray){
if (o!=null && o.equals(backingElem)){
return true;
}
}
return false;
}
public boolean containsAll(Collection<?> c){
for(E elem:(Set<E>)c){
if(!(this.contains(elem))){
return false;
}
}
return true;
}
public int hashCode(){
int sum=0;
for(E elem:backingArray){
if(elem!=null){
sum=sum+elem.hashCode();
}
}
return sum;
}
public boolean isEmpty(){
if(numElements==0){
return true;
}
else{
return false;
}
}
public boolean remove(Object o){
int i=0;
for(Object elem:backingArray){
if(o!=null && o.equals(elem)){
backingArray[i]=null;
numElements=numElements-1;
E[] newArray=Arrays.copyOf(backingArray,backingArray.length-1);
return true;
}
i=i+1;
}
return false;
}
public boolean removeAll(Collection<?> c){
for(Object elem:c){
this.remove(elem);
}
return true;
}
public boolean retainAll(Collection<?> c){
MySet<E> removalArray=new MySet<E>();
for(E arrayElem:backingArray){
if(arrayElem!= null && !(c.contains(arrayElem))){
this.remove(arrayElem);
}
}
return false;
}
public int size(){
return numElements;
}
public <T> T[] toArray(T[] a) throws ArrayStoreException,NullPointerException{
for(int i=0;i<numElements;i++){
a[i]=(T)backingArray[i];
}
for(int j=numElements;j<a.length;j++){
a[j]=null;
}
return a;
}
public Object[] toArray(){
Object[] newArray=new Object[numElements];
for(int i=0;i<numElements;i++){
newArray[i]=backingArray[i];
}
return newArray;
}
public Iterator<E> iterator(){
setIterator iterator=new setIterator();
return iterator;
}
private class setIterator implements Iterator<E>{
private int currIndex;
private E lastElement;
public setIterator(){
currIndex=0;
lastElement=null;
}
public boolean hasNext(){
while(currIndex<=numElements && backingArray[currIndex]==null){
currIndex=currIndex+1;
}
if (currIndex<=numElements){
return true;
}
return false;
}
public E next(){
E element=backingArray[currIndex];
currIndex=currIndex+1;
lastElement=element;
return element;
}
public void remove() throws UnsupportedOperationException,IllegalStateException{
if(lastElement!=null){
MySet.this.remove((Object)lastElement);
numElements=numElements-1;
}
else{
throw new IllegalStateException();
}
}
}
}
我已經能夠減少問題，但否則這件事仍然會造成問題。
爲MYSET類代碼段缺少初始行做到這一點。請添加這些。 –