Programming Tutorials

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Java program for Map

By: Saravanan in Java Tutorials on 2009年10月03日 [フレーム]

In this Tutorial we are going to see how to implement Map with arraylist. This is an example of a Map. We must import some of the packages as below.

 import java.util.AbstractMap;
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
 public class MapExample extends AbstractMap
 {
 private List listk = new ArrayList();
 private List listv = new ArrayList();
 public Object put(Object key, Object value) 
 {
 Object result = get(key);
 if (!listk.contains(key))
 {
 listk.add(key);
 listv.add(value);
 }
 else
 listv.set(listk.indexOf(key), value);
 return result;
 }
 public Object get(Object key)
 {
 if (!listk.contains(key))
 return null;
 return listv.get(listk.indexOf(key));
 }
 public Set entrySet()
 {
 Set entries = new HashSet();
 Iterator ki = listk.iterator();
 Iterator vi = listv.iterator();
 while (ki.hasNext())
 entries.add(new Map11(ki.next(), vi.next()));
 return entries;
 }
 public String toString()
 {
 StringBuffer s = new StringBuffer("{");
 Iterator ki = listk.iterator(), vi = listv.iterator();
 while (ki.hasNext())
 {
 s.append(ki.next() + "=" + vi.next());
 if (ki.hasNext())
 s.append(", ");
 }
 s.append("}");
 return s.toString();
 }
 public static void main(String[] args)
 {
 MapExample m = new MapExample();
 m.put("Netscape", "Mountain View, CA");
 m.put("Adobe", "Mountain View, CA");
 m.put("Sun", "Mountain View, CA");
 m.put("Microsoft", "Redmond, WA");
 m.put("IBM", "White Plains, NY");
 m.put("O'Reilly", "Sebastopol, CA");
 m.put("Learning Tree", "Los Angeles, CA");
 System.out.println(m);
 }
} 
class Map11 implements Entry, Comparable
 {
 Object key, value;
 Map11(Object k, Object v)
 {
 key = k;
 value = v;
 }
 public Object getKey()
 {
 return key;
 }
 public Object getValue()
 {
 return value;
 }
 public Object setValue(Object v)
 {
 Object result = value;
 value = v;
 return result;
 }
 public boolean equals(Object o) {
 return key.equals(((Map11)o).key);
 }
 public int compareTo(Object rv) {
 return ((Comparable)key).compareTo(
 ((Map11)rv).key);
 }
}

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