Android Open Source - saostar Enumerable

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License

The source code is released under:
Apache License
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Java Source Code

package net.azyobuzi.azyotter.saostar.linq;
/* ww w . ja v  a2s  .c  o m*/
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;

import net.azyobuzi.azyotter.saostar.system.Action2;
import net.azyobuzi.azyotter.saostar.system.Func2;

public abstract class Enumerable<T> {
  public static <T> Enumerable<T> empty() {
    return new Enumerable<T>() {
      @Override
      public Enumerator<T> getEnumerator() {
        return new Enumerator<T>() {
          @Override
          public boolean moveNext() {
            return false;
          }

          @Override
          public T getCurrent() {
            return null;
          }
        };
      }
    };
  }
  
  public static <T> Enumerable<T> from(final Enumerator<T> enumerator) {
    if (enumerator == null) return empty();
    
    return new Enumerable<T>() {
      @Override
      public Enumerator<T> getEnumerator() {
        return enumerator;
      }
    };
  }

  public static <T> Enumerable<T> from(final Iterable<T> source) {
    if (source == null) return empty();
    
    return from(new Enumerator<T>() {
      private Iterator<T> itr = source.iterator();
      private T current;

      @Override
      public boolean moveNext() {
        if (itr.hasNext()) {
          current = itr.next();
          return true;
        } else {
          return false;
        }
      }

      @Override
      public T getCurrent() {
        return current;
      }
    });
  }

  public static <T> Enumerable<T> from(final T[] source) {
    if (source == null) return empty();
    
    return from(new Enumerator<T>() {
      private int index = -1;
      private T current;

      @Override
      public boolean moveNext() {
        index++;

        if (source.length > index) {
          current = source[index];
          return true;
        } else {
          return false;
        }
      }

      @Override
      public T getCurrent() {
        return current;
      }
    });
  }
  
  public static <T> Enumerable<T> oneElement(final T value) {
    return from(new Enumerator<T>() {
      private boolean returned = false;

      @Override
      public boolean moveNext() {
        if (!returned) {
          returned = true;
          return true;
        } else {
          return false;
        }
      }

      @Override
      public T getCurrent() {
        return value;
      }
    });
  }

  public abstract Enumerator<T> getEnumerator();

  public void forEach(Action2<T, Integer> action) {
    Enumerator<T> enumerator = getEnumerator();
    int index = 0;
    while (enumerator.moveNext()) {
      action.invoke(enumerator.getCurrent(), index++);
    }
  }

  public ArrayList<T> toArrayList() {
    final ArrayList<T> re = new ArrayList<T>();
    forEach(new Action2<T, Integer>() {
      @Override
      public void invoke(T arg0, Integer arg1) {
        re.add(arg0);
      }
    });
    return re;
  }

  public <TResult> Enumerable<TResult> select(final Func2<T, Integer, TResult> selector) {
    return from(new Enumerator<TResult>() {
      private Enumerator<T> source = getEnumerator();
      private TResult current;
      private int index = 0;

      @Override
      public boolean moveNext() {
        if (source.moveNext()) {
          current = selector.invoke(source.getCurrent(), index++);
          return true;
        } else {
          return false;
        }
      }

      @Override
      public TResult getCurrent() {
        return current;
      }
    });
  }

  public Enumerable<T> where(final Func2<T, Integer, Boolean> predicate) {
    return from(new Enumerator<T>() {
      private Enumerator<T> source = getEnumerator();
      private T current;
      private int index = 0;

      @Override
      public boolean moveNext() {
        if (source.moveNext()) {
          boolean result = predicate.invoke(source.getCurrent(), index++);
          if (result) {
            current = source.getCurrent();
            return true;
          } else {
            return moveNext();
          }
        } else {
          return false;
        }
      }

      @Override
      public T getCurrent() {
        return current;
      }
    });
  }

  public <TResult> Enumerable<TResult> cast() {
    return select(new Func2<T, Integer, TResult>() {
      @SuppressWarnings("unchecked")
      @Override
      public TResult invoke(T arg0, Integer arg1) {
        return (TResult)arg0;
      }
    });
  }

  public T firstOrDefault(T defaultValue) {
    T result = defaultValue;

    Enumerator<T> source = getEnumerator();
    if (source.moveNext())
      result = source.getCurrent();

    return result;
  }

  public T lastOrDefault(T defaultValue) {
    T result = defaultValue;

    Enumerator<T> source = getEnumerator();
    while (source.moveNext()) {
      result = source.getCurrent();
    }

    return result;
  }

  public Enumerable<T> concat(final Enumerable<? extends T> second) {
    return from(new Enumerator<T>() {
      private T current;

      private Enumerator<T> firstEnumerator = getEnumerator();
      private Enumerator<? extends T> secondEnumerator = second.getEnumerator();

      @Override
      public boolean moveNext() {
        if (firstEnumerator.moveNext()) {
          current = firstEnumerator.getCurrent();
          return true;
        } else if (secondEnumerator.moveNext()) {
          current = secondEnumerator.getCurrent();
          return true;
        }

        return false;
      }

      @Override
      public T getCurrent() {
        return current;
      }
    });
  }

  public T elementAtOrDefault(int index, T defaultValue) {
    int i = 0;
    Enumerator<T> source = getEnumerator();
    while (source.moveNext()) {
      if (i++ == index) return source.getCurrent();
    }

    return defaultValue;
  }
  
  public Enumerable<T> union(final Enumerable<? extends T> second) {
    return from(new Enumerator<T>() {
      private T current;
      private HashSet<T> returned = new HashSet<T>();
      
      private Enumerator<T> firstEnumerator = getEnumerator();
      private Enumerator<? extends T> secondEnumerator = second.getEnumerator();

      @Override
      public boolean moveNext() {
        if (firstEnumerator.moveNext()) {
          current = firstEnumerator.getCurrent();
          return returned.add(current) ? true : moveNext();
        } else if (secondEnumerator.moveNext()) {
          current = secondEnumerator.getCurrent();
          return returned.add(current) ? true : moveNext();
        }

        return false;
      }

      @Override
      public T getCurrent() {
        return current;
      }
    });
  }
  
  public Enumerable<T> distinct() {
    return from(new Enumerator<T>() {
      private T current;
      private HashSet<T> returned = new HashSet<T>();
      
      private Enumerator<T> source = getEnumerator();

      @Override
      public boolean moveNext() {
        if (source.moveNext()) {
          current = source.getCurrent();
          return returned.add(current) ? true : moveNext();
        } else {
          return false;
        }
      }

      @Override
      public T getCurrent() {
        return current;
      }
    });
  }
  
  public Enumerable<T> distinct(final Func2<T, T, Boolean> compareEquality) {
    return from(new Enumerator<T>() {
      private T current;
      private HashSet<T> returned = new HashSet<T>();
      
      private Enumerator<T> source = getEnumerator();

      @Override
      public boolean moveNext() {
        if (source.moveNext()) {
          current = source.getCurrent();
          Enumerable<T> equal = from(returned).where(new Func2<T, Integer, Boolean>() {
            @Override
            public Boolean invoke(T arg0, Integer arg1) {
              return compareEquality.invoke(current, arg0);
            }
          });
          if (equal.firstOrDefault(null) == null) {
            returned.add(current);
            return true;
          } else {
            return moveNext();
          }
        } else {
          return false;
        }
      }

      @Override
      public T getCurrent() {
        return current;
      }
    });
  }
}
Java Source Code List
