/*
* Written by Dawid Kurzyniec, based on public domain code written by Doug Lea
* and publictly available documentation, and released to the public domain, as
* explained at http://creativecommons.org/licenses/publicdomain
*/
package net.jxta.impl.util.backport.java.util;
import java.util.Map;
import java.util.Set;
import java.util.Iterator;
/**
* Convenience base class for map implementations that provides helper classes
* representing simple map entries, both mutable and immutable.
*
* @author Doug Lea
* @author Dawid Kurzyniec
*/
@SuppressWarnings("unchecked")
public abstract class AbstractMap extends java.util.AbstractMap {
transient Set keySet;
/**
* Sole constructor. (For invocation by subclass constructors, typically
* implicit.)
*/
protected AbstractMap() {}
/**
* {@inheritDoc}
*/
public Set keySet() {
if (keySet == null) {
keySet = new AbstractSet() { // from e.e.m.b. (overrides toArray)
public int size() { return AbstractMap.this.size(); }
public boolean contains(Object e) { return AbstractMap.this.containsKey(e); }
public Iterator iterator() {
return new Iterator() {
final Iterator itr = AbstractMap.this.entrySet().iterator();
public boolean hasNext() { return itr.hasNext(); }
public Object next() { return ((Entry)itr.next()).getKey(); }
public void remove() { itr.remove(); }
};
}
};
}
return keySet;
}
/**
* An Entry maintaining a key and a value. The value may be
* changed using the <tt>setValue</tt> method. This class
* facilitates the process of building custom map
* implementations. For example, it may be convenient to return
* arrays of <tt>SimpleEntry</tt> instances in method
* <tt>Map.entrySet().toArray</tt>
*
* @since 1.6
*/
public static class SimpleEntry implements Entry {
private final Object key;
private Object value;
/**
* Creates an entry representing a mapping from the specified
* key to the specified value.
*
* @param key the key represented by this entry
* @param value the value represented by this entry
*/
public SimpleEntry(Object key, Object value) {
this.key = key;
this.value = value;
}
/**
* Creates an entry representing the same mapping as the
* specified entry.
*
* @param entry the entry to copy
*/
public SimpleEntry(Entry entry) {
this.key = entry.getKey();
this.value = entry.getValue();
}
/**
* Returns the key corresponding to this entry.
*
* @return the key corresponding to this entry
*/
public Object getKey() {
return key;
}
/**
* Returns the value corresponding to this entry.
*
* @return the value corresponding to this entry
*/
public Object getValue() {
return value;
}
/**
* Replaces the value corresponding to this entry with the specified
* value.
*
* @param value new value to be stored in this entry
* @return the old value corresponding to the entry
*/
public Object setValue(Object value) {
Object oldValue = this.value;
this.value = value;
return oldValue;
}
public boolean equals(Object o) {
if (!(o instanceof Map.Entry)) return false;
Map.Entry e = (Map.Entry)o;
return eq(key, e.getKey()) && eq(value, e.getValue());
}
public int hashCode() {
return ((key == null) ? 0 : key.hashCode()) ^
((value == null) ? 0 : value.hashCode());
}
/**
* Returns a String representation of this map entry. This
* implementation returns the string representation of this
* entry's key followed by the equals character ("<tt>=</tt>")
* followed by the string representation of this entry's value.
*
* @return a String representation of this map entry
*/
public String toString() {
return key + "=" + value;
}
}
/**
* An Entry maintaining an immutable key and value, This class
* does not support method <tt>setValue</tt>. This class may be
* convenient in methods that return thread-safe snapshots of
* key-value mappings.
*
* @since 1.6
*/
public static class SimpleImmutableEntry implements Entry {
private final Object key;
private final Object value;
/**
* Creates an entry representing a mapping from the specified
* key to the specified value.
*
* @param key the key represented by this entry
* @param value the value represented by this entry
*/
public SimpleImmutableEntry(Object key, Object value) {
this.key = key;
this.value = value;
}
/**
* Creates an entry representing the same mapping as the
* specified entry.
*
* @param entry the entry to copy
*/
public SimpleImmutableEntry(Entry entry) {
this.key = entry.getKey();
this.value = entry.getValue();
}
/**
* Returns the key corresponding to this entry.
*
* @return the key corresponding to this entry
*/
public Object getKey() {
return key;
}
/**
* Returns the value corresponding to this entry.
*
* @return the value corresponding to this entry
*/
public Object getValue() {
return value;
}
/**
* Replaces the value corresponding to this entry with the specified
* value (optional operation). This implementation simply throws
* <tt>UnsupportedOperationException</tt>, as this class implements
* an <i>immutable</i> map entry.
*
* @param value new value to be stored in this entry
* @return (Does not return)
* @throws UnsupportedOperationException always
*/
public Object setValue(Object value) {
throw new UnsupportedOperationException();
}
public boolean equals(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry)o;
return eq(key, e.getKey()) && eq(value, e.getValue());
}
public int hashCode() {
return ((key == null) ? 0 : key.hashCode()) ^
((value == null) ? 0 : value.hashCode());
}
/**
* Returns a String representation of this map entry. This
* implementation returns the string representation of this
* entry's key followed by the equals character ("<tt>=</tt>")
* followed by the string representation of this entry's value.
*
* @return a String representation of this map entry
*/
public String toString() {
return key + "=" + value;
}
}
private static boolean eq(Object o1, Object o2) {
return (o1 == null ? o2 == null : o1.equals(o2));
}
}