在Java中将Hashtable设为只读
只读Hashtable意味着用户将无法在其中添加或删除元素。让我们首先创建具有键值对的Hashtable-
Hashtable<String, String>hash = new Hashtable<String, String>();
hash.put("1", "A");
hash.put("2", "B");
hash.put("3", "C");
hash.put("4", "D");
hash.put("5", "E");
hash.put("6", "F");
hash.put("7", "G");现在，使用unmodifiableMap()形成一个Hashtable只读-
Map<String, String>m = Collections.unmodifiableMap(hash);
示例
import java.util.Collections;
import java.util.Hashtable;
import java.util.Map;
public class Demo {
public static void main(String[] s) {
Hashtable<String, String>hash = new Hashtable<String, String>();
hash.put("1", "A");
hash.put("2", "B");
hash.put("3", "C");
hash.put("4", "D");
hash.put("5", "E");
hash.put("6", "F");
hash.put("7", "G");
hash.put("8", "H");
hash.put("9", "I");
hash.put("10", "J");
System.out.println("Hashtable = " + hash);
Map<String, String>m = Collections.unmodifiableMap(hash);
System.out.println("Hashtable is now read-only!");
}
}输出结果
Hashtable = {9=I, 8=H, 7=G, 6=F, 5=E, 4=D, 3=C, 2=B, 10=J, 1=A}
Hashtable is now read-only!