MultiMap extends AbstractMap
import java.util.*;
public class MultiMap extends AbstractMap {
private Map map;
public MultiMap() {
this(null);
}
public MultiMap(Map copy) {
map = new HashMap();
if (copy != null) {
Iterator iter = copy.entrySet().iterator();
while(iter.hasNext()) {
Map.Entry entry = (Map.Entry)iter.next();
add(entry.getKey(), entry.getValue());
}
}
}
public boolean containsKey(Object key) {
Collection values = (Collection)map.get(key);
return ((values != null) && (values.size() != 0));
}
public boolean containsValue(Object value) {
Iterator iter = map.entrySet().iterator();
boolean found = false;
while (iter.hasNext()) {
Map.Entry entry = (Map.Entry)iter.next();
Collection values = (Collection)entry.getValue();
if (values.contains(value)) {
found = true;
break;
}
}
return found;
}
public Object get(Object key) {
return map.get(key);
}
public Object put(Object key, Object value) {
if (!(value instanceof Collection)) {
throw new IllegalArgumentException(value.getClass().toString());
}
Object original = get(key);
map.put(key, value);
return original;
}
public boolean add(Object key, Object value) {
return getValues(key).add(value);
}
public boolean addAll(Object key, Collection values) {
return getValues(key).addAll(values);
}
private Collection getValues(Object key) {
Collection col = (Collection)map.get(key);
if (col == null) {
col = new HashSet();
map.put(key, col);
}
return col;
}
public Object remove(Object key) {
Object original = get(key);
map.remove(key);
return original;
}
public boolean remove(Object key, Object value) {
Collection values = (Collection)map.get(key);
if (values == null) {
return false;
} else {
return values.remove(value);
}
}
public void clear() {
map.clear();
}
public String toString() {
StringBuffer buff = new StringBuffer();
buff.append("{");
Iterator keys = map.keySet().iterator();
boolean first = true;
while (keys.hasNext()) {
if (first) {
first = false;
} else {
buff.append(", ");
}
Object key = keys.next();
Collection values = getValues(key);
buff.append("[" + key + ": " + values + "]");
}
buff.append("}");
return buff.toString();
}
public Set entrySet() {
int size = 0;
Iterator iterKeys = map.entrySet().iterator();
while (iterKeys.hasNext()) {
Map.Entry entry = (Map.Entry)iterKeys.next();
Collection values = (Collection)entry.getValue();
Iterator iterValues = values.iterator();
while (iterValues.hasNext()) {
size++;
iterValues.next();
}
}
final int finalSize = size;
final Iterator entries = map.entrySet().iterator();
return new AbstractSet() {
int pos = 0;
Map.Entry entry;
Iterator values;
public Iterator iterator() {
return new Iterator() {
public void remove() {
throw new UnsupportedOperationException();
}
public boolean hasNext() {
return pos != finalSize;
}
public Object next() {
while(true) {
if (entry == null) {
entry = (Map.Entry)entries.next();
values = ((Collection)entry.getValue()).iterator();
}
Object key = entry.getKey();
if (values.hasNext()) {
Object value = values.next();
pos++;
return new Entry(key, value);
} else {
entry = null;
}
}
}
};
}
public int size() {
return finalSize;
}
};
}
private static class Entry implements Map.Entry {
Object key;
Object value;
Entry(Object key, Object value) {
this.key = key;
this.value = value;
}
public Object getKey() {
return key;
}
public Object getValue() {
return value;
}
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;
} else {
Map.Entry e = (Map.Entry)o;
return (key==null ? e.getKey()==null : key.equals(e.getKey())) &&
(value==null ? e.getValue()==null : value.equals(e.getValue()));
}
}
public int hashCode() {
return ((value==null) ? 0 : value.hashCode());
}
public String toString() {
return key+"="+value;
}
}
public static void main (String args[]) {
Map map = new HashMap();
map.put("one", "two");
map.put("three", "four");
map.put("five", "six");
MultiMap multi = new MultiMap(map);
System.out.println(multi);
multi.add("five", "seven");
multi.add("five", "eight");
multi.add("five", "nine");
multi.add("five", "ten");
multi.add("three", "seven");
System.out.println(multi);
multi.remove("three");
System.out.println(multi);
}
}
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