Mega Code Archive
Implements Map
<![CDATA[
/*
You asked about Google.
They are located in: null
Key Adobe; Value Mountain View, CA
Key IBM; Value White Plains, NY
Key Learning Tree; Value Los Angeles, CA
entrySet() returns 3 Map.Entry's*/
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;
import java.util.TreeSet;
public class MainClass {
public static void main(String[] argv) {
Map map = new MyMap();
map.put("Adobe", "Mountain View, CA");
map.put("Learning Tree", "Los Angeles, CA");
map.put("IBM", "White Plains, NY");
String queryString = "Google";
System.out.println("You asked about " + queryString + ".");
String resultString = (String) map.get(queryString);
System.out.println("They are located in: " + resultString);
System.out.println();
Iterator k = map.keySet().iterator();
while (k.hasNext()) {
String key = (String) k.next();
System.out.println("Key " + key + "; Value " + (String) map.get(key));
}
Set es = map.entrySet();
System.out.println("entrySet() returns " + es.size() + " Map.Entry's");
}
}
class MyMap implements Map {
private ArrayList keys;
private ArrayList values;
public MyMap() {
keys = new ArrayList();
values = new ArrayList();
}
/** Return the number of mappings in this Map. */
public int size() {
return keys.size();
}
/** Return true if this map is empty. */
public boolean isEmpty() {
return size() == 0;
}
/** Return true if o is contained as a Key in this Map. */
public boolean containsKey(Object o) {
return keys.contains(o);
}
/** Return true if o is contained as a Value in this Map. */
public boolean containsValue(Object o) {
return keys.contains(o);
}
/** Get the object value corresponding to key k. */
public Object get(Object k) {
int i = keys.indexOf(k);
if (i == -1)
return null;
return values.get(i);
}
/**
* Put the given pair (k, v) into this map, by maintaining "keys" in sorted
* order.
*/
public Object put(Object k, Object v) {
for (int i = 0; i < keys.size(); i++) {
Object old = keys.get(i);
/* Does the key already exist? */
if (((Comparable) k).compareTo(keys.get(i)) == 0) {
keys.set(i, v);
return old;
}
/*
* Did we just go past where to put it? i.e., keep keys in sorted order.
*/
if (((Comparable) k).compareTo(keys.get(i)) == +1) {
int where = i > 0 ? i - 1 : 0;
keys.add(where, k);
values.add(where, v);
return null;
}
}
// Else it goes at the end.
keys.add(k);
values.add(v);
return null;
}
/** Put all the pairs from oldMap into this map */
public void putAll(java.util.Map oldMap) {
Iterator keysIter = oldMap.keySet().iterator();
while (keysIter.hasNext()) {
Object k = keysIter.next();
Object v = oldMap.get(k);
put(k, v);
}
}
public Object remove(Object k) {
int i = keys.indexOf(k);
if (i == -1)
return null;
Object old = values.get(i);
keys.remove(i);
values.remove(i);
return old;
}
public void clear() {
keys.clear();
values.clear();
}
public java.util.Set keySet() {
return new TreeSet(keys);
}
public java.util.Collection values() {
return values;
}
/**
* The Map.Entry objects contained in the Set returned by entrySet().
*/
private class MyMapEntry implements Map.Entry, Comparable {
private Object key, value;
MyMapEntry(Object k, Object v) {
key = k;
value = v;
}
public Object getKey() {
return key;
}
public Object getValue() {
return value;
}
public Object setValue(Object nv) {
throw new UnsupportedOperationException("setValue");
}
public int compareTo(Object o2) {
if (!(o2 instanceof MyMapEntry))
throw new IllegalArgumentException("Huh? Not a MapEntry?");
Object otherKey = ((MyMapEntry) o2).getKey();
return ((Comparable) key).compareTo((Comparable) otherKey);
}
}
/** The set of Map.Entry objects returned from entrySet(). */
private class MyMapSet extends AbstractSet {
List list;
MyMapSet(ArrayList al) {
list = al;
}
public Iterator iterator() {
return list.iterator();
}
public int size() {
return list.size();
}
}
/**
* Returns a set view of the mappings contained in this Map. Each element in
* the returned set is a Map.Entry. NOT guaranteed fully to implement the
* contract of entrySet declared in java.util.Map.
*/
public java.util.Set entrySet() {
if (keys.size() != values.size())
throw new IllegalStateException("InternalError: keys and values out of sync");
ArrayList al = new ArrayList();
for (int i = 0; i < keys.size(); i++) {
al.add(new MyMapEntry(keys.get(i), values.get(i)));
}
return new MyMapSet(al);
}
}
]]>