/*Explicit Exceptions:
* We can also throw our own exceptions using the throw keyword.
*1) Can provide more information message to a user.
*2) Can provide more information to code that "catches " the exceptions.
*/
/*The Enhanced For Loop
* Java allows us to iterate through Lists and Sets using
* a convenient shorthand syntax sometimes called the
* "foreeach" or "enhanced for" loop.
*/
/*For-each Iteration And ArraySets
*To support theenchanced for loop,
we need to make ArraySet implements.
*There are also some default methods in Iterable, not shown.
*
* public interfce Iterator<T> {
* Iterator<T> iterator();
*
* }
*
*/
import java.util.HashSet;
import java.util.Set;
import java.util.Iterator;
public class ArraySet<T>
implements Iterable<T>
{
private T[] items;
private int size;
public ArraySet() {
items = (T[])
new Object[100
];
size = 0
;
}
/*Returns true if this map contains a mapping for the specified key*/
public boolean contains(T x) {
for(
int i = 0; i < size; i+= 1
) {
if(items[i] ==
null) {
if(x ==
null) {
return true;
}
}
if(x.equals(items[i])) {
return true;
}
}
return false;
}
public void add(T x) {
if(x ==
null) {
throw new IllegalArgumentException("You can't add null to an ArraySet"
);
}
if(contains(x)) {
return;
}
items[size] =
x;
size += 1
;
}
public int size() {
return size;
}
/**returns an iterator into ME. */
public Iterator<T>
iterator() {
return new ArraySetIterator();
}
/*public interface Iterator <T> {
* boolean hasNext();
* T next();
* }
*/
private class ArraySetIterator
implements Iterator<T>
{
private int wizPos;
public ArraySetIterator() {
wizPos = 0
;
}
public boolean hasNext() {
return wizPos <
size;
}
public T next() {
T returnItem =
items[wizPos];
wizPos += 1
;
return returnItem;
}
}
/*The toString() method provides a string representation
* of an object.
*
*System.out.println(Object x) calls x.toString();
The default toString() is the name of the class, @,memory location
of the object;
*/
@Override
public String toString() {
// String returnString = "{";
StringBuilder returnSB =
new StringBuilder("{"
);
for(
int i = 0; i < size-1; i+=1
) {
returnSB.append(items[i].toString());
returnSB.append( ", "
);
}
returnSB.append(items[size-1
]);
returnSB.append( "}"
);
return returnSB.toString();
/* for(T item : this) {
returnString += item.toString();
returnString += ",";
}*/
}
/* Equals vs. ==
* == compares the bits. For reference, == means "referencing the same object"
*
*/
@Override
public boolean equals(Object other){
if(
this == other) {
return true; }
if(other ==
null) {
return false; }
if (other.getClass() !=
this.getClass()) {
return false;
}
ArraySet<T> o = (ArraySet<T>
) other;
if (o.size() !=
this.size()) {
return false;
}
for(T item :
this) {
if(!
o.contains(item)) {
return false;
}
}
return true;
}
public static void main(String[] args) {
/*Set<Integer> javaset = new HashSet<>();
javaset.add(5);
javaset.add(23);
javaset.add(42);
Iterator<Integer> seer = javaset.iterator();
while(seer.hasNext()) {
int i = seer.next();
System.out.println(i);
}*/
ArraySet<Integer> aset =
new ArraySet<>
();
aset.add(5
);
aset.add(23
);
aset.add(42
);
System.out.println(aset);
Iterator<Integer> aseer =
aset.iterator();
/* while(aseer.hasNext()) {
int i = aseer.next();
System.out.println(i);
}
for(int i : aset){
System.out.println(i);
}*/
System.out.println(aset.equals(null));
System.out.println(aset.equals("fish"
) );
System.out.println(aset.equals(aset));
/* ArraySet<String> s = new ArraySet<>();
s.add(null);
s.add("horse");
s.add("fish");
s.add("house");
s.add("fish");
System.out.println(s.contains("horse"));
System.out.println(s.size());*/
}
}
转载于:https://www.cnblogs.com/Shinered/p/10465626.html
