Category: Java

How can an enum have abstract methods?

Posted on by damrakoc

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public enum RecyclerViewLayoutManager {
LINEAR {
  public ViewGroup.LayoutParams getLayoutParams() {
   return new LinearLayout.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  }
 
  ;
},
GRID {
  public ViewGroup.LayoutParams getLayoutParams() {
   return new GridLayoutManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  }
 
  ;
},
STAGGERED {
  public ViewGroup.LayoutParams getLayoutParams() {
   return new StaggeredGridLayoutManager.LayoutParams(ViewGroup.LayoutParams.MATCH_PARENT, ViewGroup.LayoutParams.WRAP_CONTENT);
  }
 
  ;
};
 
public abstract ViewGroup.LayoutParams getLayoutParams();
}

 

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Thread Safe Singleton Abstract class

Posted on by damrakoc

Thread Safe Singleton Abstract class

Thread Safe Singleton Abstract class
Java
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package com.damrakoc.java;
 
import android.util.Log;
 
import java.lang.reflect.Constructor;
import java.util.HashMap;
import java.util.Map;
 
/**
* Created by damra on 08/08/2017.
*
USAGE:
public class TestSingleton extends ThreadSafeSingleton<TestSingleton> {
    public static TestSingleton getInstance() {
        return ThreadSafeSingleton.getInstance(TestSingleton.class);
    }
}
 
*/
 
@SuppressWarnings({"all"})
public abstract class ThreadSafeSingleton<T> {
 
    private static final Map<Class<? extends ThreadSafeSingleton>, ThreadSafeSingleton> INSTANCES = new HashMap<>();
    private static final String TAG = ThreadSafeSingleton.class.getSimpleName();
 
    private static class SingletonHolder<T> {
        private static <T> T getInstance(Class<T> clazz){
            Constructor<T> constructor = (Constructor<T>) clazz.getDeclaredConstructors()[0];
            constructor.setAccessible(true);
 
            try{
                return constructor.newInstance(null);
            }catch (Exception e){
                Log.d(TAG, "getInstance: "+e.getLocalizedMessage());
                return null;
            }
        }
    }
 
    protected ThreadSafeSingleton() {
        Log.d(TAG, "Initializing ThreadSafeSingleton");
    }
 
    protected static <T extends ThreadSafeSingleton<T>> T getInstance(Class<T> clazz) {
        if(INSTANCES.containsKey(clazz)) {
            return (T) INSTANCES.get(clazz);
        } else {
 
            try{
                T instance = SingletonHolder.getInstance(clazz);
                INSTANCES.put(clazz, instance);
                return instance;
            }catch (Exception e ){
                return null;
            }
        }
    }
 
    protected static <T extends ThreadSafeSingleton<T>> void putInstance(Class<T> clazz, T instance) {
        if(!INSTANCES.containsKey(clazz)) {
            INSTANCES.put(clazz, instance);
        }
    }
}

 

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