MultiMap.java Source code

Introduction

Here is the source code for MultiMap.java

Source

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);
    }
}