java.util.Collections.unmodifiableMap() 方法
package com.codingdict;
import java.util.*;
public class CollectionsDemo {
public static void main(String[] s) {
//object hash table
Hashtable<String,String> table = new Hashtable<String,String>();
// populate the table
table.put("key1", "value1");
table.put("key2", "value2");
table.put("key3", "value3");
System.out.println("Initial collection: "+table);
// create unmodifiable map
Map m = Collections.unmodifiableMap(table);
// try to modify the collection
m.put("key3", "value3");
}
}