Try.java

/**
 * Copyright 2008 - 2015 The Loon Game Engine Authors
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 * 
 * @project loon
 * @author cping
 * @email：javachenpeng@yahoo.com
 * @version 0.5
 */
package loon.utils.reply;

public abstract class Try<T> {

    public static final class Success<T> extends Try<T> {
        public final T value;
        public Success (T value) {
            this.value = value;
        }

        @Override public T get () { return value; }
        @Override public Throwable getFailure () { throw new IllegalStateException(); }
        @Override public boolean isSuccess () { return true; }
        @Override public <R> Try<R> map (Function<? super T, R> func) {
            try {
                return success(func.apply(value));
            } catch (Throwable t) {
                return failure(t);
            }
        }
        @Override public <R> Try<R> flatMap (Function<? super T, Try<R>> func) {
            try {
                return func.apply(value);
            } catch (Throwable t) {
                return failure(t);
            }
        }

        @Override public String toString () { return "Success(" + value + ")"; }
    }

    public static final class Failure<T> extends Try<T> {
        public final Throwable cause;
        public Failure (Throwable cause) {
            this.cause = cause;
        }

        @Override public T get () {
            if (cause instanceof RuntimeException) {
                throw (RuntimeException)cause;
            } else if (cause instanceof Error) {
                throw (Error)cause;
            } else {
                throw (RuntimeException)new RuntimeException().initCause(cause);
            }
        }
        @Override public Throwable getFailure () { return cause; }
        @Override public boolean isSuccess () { return false; }
        @Override public <R> Try<R> map (Function<? super T, R> func) {
            return this.<R>casted();
        }
        @Override public <R> Try<R> flatMap (Function<? super T, Try<R>> func) {
            return this.<R>casted();
        }

        @Override public String toString () { return "Failure(" + cause + ")"; }

        @SuppressWarnings("unchecked") private <R> Try<R> casted () { return (Try<R>)this; }
    }

    public static <T> Try<T> success (T value) { return new Success<T>(value); }

    public static <T> Try<T> failure (Throwable cause) { return new Failure<T>(cause); }

    public static <T,R> Function<Try<T>,Try<R>> lift (final Function<? super T, R> func) {
        return new Function<Try<T>,Try<R>>() {
            public Try<R> apply (Try<T> result) { return result.map(func); }
        };
    }

    public abstract T get ();

    public abstract Throwable getFailure ();

    public abstract boolean isSuccess ();

    public boolean isFailure () { return !isSuccess(); }

    public abstract <R> Try<R> map (Function<? super T, R> func);

    public abstract <R> Try<R> flatMap (Function<? super T, Try<R>> func);

    private Try () {}
}