MainClass.java Source code

Introduction

Here is the source code for MainClass.java

Source

/*
 Output:
    
{Virginia=Richmond, Massachusetts=Boston, New York=Albany}
[Virginia, Massachusetts, New York]
[Richmond, Boston, Albany]
    
    
    
 * */

import java.io.Serializable;
import java.util.AbstractMap;
import java.util.AbstractSet;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;

public class MainClass {
    public static void main(String args[]) {
        AbstractMap map = new ArrayMap(13);
        map.put("Virginia", "Richmond");
        map.put("Massachusetts", "Boston");
        map.put("New York", "Albany");
        System.out.println(map);
        System.out.println(map.keySet());
        System.out.println(map.values());
    }
}

class ArrayMap extends AbstractMap implements Cloneable, Serializable {

    static class Entry implements Map.Entry {
        protected Object key, value;

        public 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 newValue) {
            Object oldValue = value;
            value = newValue;
            return oldValue;
        }

        public boolean equals(Object o) {
            if (!(o instanceof Map.Entry)) {
                return false;
            }
            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() {
            int keyHash = (key == null ? 0 : key.hashCode());
            int valueHash = (value == null ? 0 : value.hashCode());
            return keyHash ^ valueHash;
        }

        public String toString() {
            return key + "=" + value;
        }
    }

    private Set entries = null;

    private ArrayList list;

    public ArrayMap() {
        list = new ArrayList();
    }

    public ArrayMap(Map map) {
        list = new ArrayList();
        putAll(map);
    }

    public ArrayMap(int initialCapacity) {
        list = new ArrayList(initialCapacity);
    }

    public Set entrySet() {
        if (entries == null) {
            entries = new AbstractSet() {
                public void clear() {
                    list.clear();
                }

                public Iterator iterator() {
                    return list.iterator();
                }

                public int size() {
                    return list.size();
                }
            };
        }
        return entries;
    }

    public Object put(Object key, Object value) {
        int size = list.size();
        Entry entry = null;
        int i;
        if (key == null) {
            for (i = 0; i < size; i++) {
                entry = (Entry) (list.get(i));
                if (entry.getKey() == null) {
                    break;
                }
            }
        } else {
            for (i = 0; i < size; i++) {
                entry = (Entry) (list.get(i));
                if (key.equals(entry.getKey())) {
                    break;
                }
            }
        }
        Object oldValue = null;
        if (i < size) {
            oldValue = entry.getValue();
            entry.setValue(value);
        } else {
            list.add(new Entry(key, value));
        }
        return oldValue;
    }

    public Object clone() {
        return new ArrayMap(this);
    }

}