Update #0 - First Release

sources/main/java/com/google/common/base/AbstractIterator.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2007 The Guava 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.
+ */
+
+package com.google.common.base;
+
+import static com.google.common.base.Preconditions.checkState;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+import com.google.common.annotations.GwtCompatible;
+
+/**
+ * Note this class is a copy of
+ * {@link com.google.common.collect.AbstractIterator} (for dependency reasons).
+ */
+@GwtCompatible
+abstract class AbstractIterator<T> implements Iterator<T> {
+	private State state = State.NOT_READY;
+
+	protected AbstractIterator() {
+	}
+
+	private enum State {
+		READY, NOT_READY, DONE, FAILED,
+	}
+
+	private T next;
+
+	protected abstract T computeNext();
+
+	protected final T endOfData() {
+		state = State.DONE;
+		return null;
+	}
+
+	@Override
+	public final boolean hasNext() {
+		checkState(state != State.FAILED);
+		switch (state) {
+		case DONE:
+			return false;
+		case READY:
+			return true;
+		default:
+		}
+		return tryToComputeNext();
+	}
+
+	private boolean tryToComputeNext() {
+		state = State.FAILED; // temporary pessimism
+		next = computeNext();
+		if (state != State.DONE) {
+			state = State.READY;
+			return true;
+		}
+		return false;
+	}
+
+	@Override
+	public final T next() {
+		if (!hasNext()) {
+			throw new NoSuchElementException();
+		}
+		state = State.NOT_READY;
+		T result = next;
+		next = null;
+		return result;
+	}
+
+	@Override
+	public final void remove() {
+		throw new UnsupportedOperationException();
+	}
+}