how to access object inside static block

[Smilemaggy Rajendran]

I have intialized Hash map inside static block, I need to access the hashmap object to get the value using key it inside my getExpo method.

My class goes here

public class ExampleFactory {

static
{
HashMap<String,Class<?>> hmap = new HashMap<String,Class<?>>();

hmap.put("app", application.class);
hmap.put("expo", expession.class);

}

public void getExpo(String key,String expression)
{

// I need to access the object in static block

Class aclass=(Class) hmap.get(key); // it works when i place the hashmap intialization inside main method but not working when i place Hashmap initialiastion in static block

return null;


}

[Jeff Verdegan]

Move the declaration outside of the static initializer and just keep the put() calls inside.

class Foo {
  private static Map<X> map = new HashMap<X>();

  static {
    map.put(a, b);
    map.put(c, d);
  }
}

[Rob Spoor]

If the Map shouldn't change after it's initialized, you can add some safety to ensure it doesn't change:

class Foo {
  private static final Map<X> map; // final; will be initialized inside the static initializer

  static {
    Map<X> m = new HashMap<X>();
    m.put(a, b);
    m.put(c, d);
    // now initialize map
    map = Collections.unmodifiableMap(m);
  }
}

Since there is no reference to the actual HashMap, the only way to access its contents is through the unmodifiable (i.e. read-only) map field. It's also made final to prevent it from being overwritten completely.

[Jeff Verdegan]

There's also this atrocity, which uses an anonymous subclass of HashMap and that class's instance initalizer. Yuck.

class Foo {
  private static final Map<X> = Collections.unmodifiableMap<X>(new HashMap<X>() {
    {
      put("abc", "123");
      put("xyz", "456");
    }
  });
}

[Rob Spoor]

That's just evil.