Java泛型问题

Question

如何在此程序中实现泛型,因此我不必在此行中转换为String:

String d = (String) h.get ("Dave");






import java.util.*;

public class TestHashTable {


  public static void main (String[] argv)
  {
    Hashtable h = new Hashtable ();

    // Insert a string and a key.
    h.put ("Ali", "Anorexic Ali");
    h.put ("Bill", "Bulimic Bill");
    h.put ("Chen", "Cadaverous Chen");
    h.put ("Dave", "Dyspeptic Dave");

    String d = (String) h.get ("Dave");
    System.out.println (d);  // Prints "Dyspeptic Dave"
  }

}

Answer 1

你可以使用a Hashtable但不鼓励使用它Map并且HashMap:

public static void main (String[] argv) {
  Map<String, String> h = new HashMap<String, String>();

  // Insert a string and a key.
  h.put("Ali", "Anorexic Ali");
  h.put("Bill", "Bulimic Bill");
  h.put("Chen", "Cadaverous Chen");
  h.put("Dave", "Dyspeptic Dave");

  String d = h.get("Dave");
  System.out.println (d);  // Prints "Dyspeptic Dave"
}

您可以用以下内容替换声明:

Map<String, String> h = new Hashtable<String, String>();

通常,如果这是一个选项,您希望在具体类上使用接口作为变量声明,参数声明和返回类型.