Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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 java.nio; /** A buffer of doubles. * <p> * A double buffer can be created in either one of the following ways: * </p> * <ul> * <li>{@link #allocate(int) Allocate} a new double array and create a buffer based on it;</li> * <li>{@link #wrap(double[]) Wrap} an existing double array to create a new buffer;</li> * <li>Use {@link java.nio.ByteBuffer#asDoubleBuffer() ByteBuffer.asDoubleBuffer} to create a double buffer based on a byte buffer. * </li> * </ul> * * @since Android 1.0 */ public abstract class DoubleBuffer extends Buffer implements Comparable<DoubleBuffer> { /** Creates a double buffer based on a newly allocated double array. * * @param capacity the capacity of the new buffer. * @return the created double buffer. * @throws IllegalArgumentException if {@code capacity} is less than zero. * @since Android 1.0 */ public static DoubleBuffer allocate(int capacity) { if (capacity < 0) { throw new IllegalArgumentException(); } return BufferFactory.newDoubleBuffer(capacity); } /** Creates a new double buffer by wrapping the given double array. * <p> * Calling this method has the same effect as {@code wrap(array, 0, array.length)}. * </p> * * @param array the double array which the new buffer will be based on. * @return the created double buffer. * @since Android 1.0 */ public static DoubleBuffer wrap(double[] array) { return wrap(array, 0, array.length); } /** Creates a new double buffer by wrapping the given double array. * <p> * The new buffer's position will be {@code start}, limit will be {@code start + len}, capacity will be the length of the array. * </p> * * @param array the double array which the new buffer will be based on. * @param start the start index, must not be negative and not greater than {@code array.length}. * @param len the length, must not be negative and not greater than {@code array.length - start}. * @return the created double buffer. * @exception IndexOutOfBoundsException if either {@code start} or {@code len} is invalid. * @since Android 1.0 */ public static DoubleBuffer wrap(double[] array, int start, int len) { int length = array.length; if (start < 0 || len < 0 || (long) start + (long) len > length) { throw new IndexOutOfBoundsException(); } DoubleBuffer buf = BufferFactory.newDoubleBuffer(array); buf.position = start; buf.limit = start + len; return buf; } /** Constructs a {@code DoubleBuffer} with given capacity. * * @param capacity the capacity of the buffer. */ DoubleBuffer(int capacity) { super(capacity); } /** Returns the double array which this buffer is based on, if there is one. * * @return the double array which this buffer is based on. * @exception ReadOnlyBufferException if this buffer is based on an array but it is read-only. * @exception UnsupportedOperationException if this buffer is not based on an array. * @since Android 1.0 */ public final double[] array() { return protectedArray(); } /** Returns the offset of the double array which this buffer is based on, if there is one. * <p> * The offset is the index of the array corresponding to the zero position of the buffer. * </p> * * @return the offset of the double array which this buffer is based on. * @exception ReadOnlyBufferException if this buffer is based on an array, but it is read-only. * @exception UnsupportedOperationException if this buffer is not based on an array. * @since Android 1.0 */ public final int arrayOffset() { return protectedArrayOffset(); } /** Returns a read-only buffer that shares its content with this buffer. * <p> * The returned buffer is guaranteed to be a new instance, even if this buffer is read-only itself. The new buffer's position, * limit, capacity and mark are the same as this buffer's. * </p> * <p> * The new buffer shares its content with this buffer, which means that this buffer's change of content will be visible to the * new buffer. The two buffer's position, limit and mark are independent. * </p> * * @return a read-only version of this buffer. * @since Android 1.0 */ public abstract DoubleBuffer asReadOnlyBuffer(); /** Compacts this double buffer. * <p> * The remaining doubles will be moved to the head of the buffer, staring from position zero. Then the position is set to * {@code remaining()}; the limit is set to capacity; the mark is cleared. * </p> * * @return this buffer. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public abstract DoubleBuffer compact(); /** Compare the remaining doubles of this buffer to another double buffer's remaining doubles. * * @param otherBuffer another double buffer. * @return a negative value if this is less than {@code other}; 0 if this equals to {@code other}; a positive value if this is * greater than {@code other}. * @exception ClassCastException if {@code other} is not a double buffer. * @since Android 1.0 */ public int compareTo(DoubleBuffer otherBuffer) { int compareRemaining = (remaining() < otherBuffer.remaining()) ? remaining() : otherBuffer.remaining(); int thisPos = position; int otherPos = otherBuffer.position; // BEGIN android-changed double thisDouble, otherDouble; while (compareRemaining > 0) { thisDouble = get(thisPos); otherDouble = otherBuffer.get(otherPos); // checks for double and NaN inequality if ((thisDouble != otherDouble) && ((thisDouble == thisDouble) || (otherDouble == otherDouble))) { return thisDouble < otherDouble ? -1 : 1; } thisPos++; otherPos++; compareRemaining--; } // END android-changed return remaining() - otherBuffer.remaining(); } /** Returns a duplicated buffer that shares its content with this buffer. * <p> * The duplicated buffer's position, limit, capacity and mark are the same as this buffer's. The duplicated buffer's read-only * property and byte order are the same as this buffer's, too. * </p> * <p> * The new buffer shares its content with this buffer, which means either buffer's change of content will be visible to the * other. The two buffer's position, limit and mark are independent. * </p> * * @return a duplicated buffer that shares its content with this buffer. * @since Android 1.0 */ public abstract DoubleBuffer duplicate(); /** Checks whether this double buffer is equal to another object. * <p> * If {@code other} is not a double buffer then {@code false} is returned. Two double buffers are equal if and only if their * remaining doubles are exactly the same. Position, limit, capacity and mark are not considered. * </p> * * @param other the object to compare with this double buffer. * @return {@code true} if this double buffer is equal to {@code other}, {@code false} otherwise. * @since Android 1.0 */ public boolean equals(Object other) { if (!(other instanceof DoubleBuffer)) { return false; } DoubleBuffer otherBuffer = (DoubleBuffer) other; if (remaining() != otherBuffer.remaining()) { return false; } int myPosition = position; int otherPosition = otherBuffer.position; boolean equalSoFar = true; while (equalSoFar && (myPosition < limit)) { equalSoFar = get(myPosition++) == otherBuffer.get(otherPosition++); } return equalSoFar; } /** Returns the double at the current position and increases the position by 1. * * @return the double at the current position. * @exception BufferUnderflowException if the position is equal or greater than limit. * @since Android 1.0 */ public abstract double get(); /** Reads doubles from the current position into the specified double array and increases the position by the number of doubles * read. * <p> * Calling this method has the same effect as {@code get(dest, 0, dest.length)}. * </p> * * @param dest the destination double array. * @return this buffer. * @exception BufferUnderflowException if {@code dest.length} is greater than {@code remaining()}. * @since Android 1.0 */ public DoubleBuffer get(double[] dest) { return get(dest, 0, dest.length); } /** Reads doubles from the current position into the specified double array, starting from the specified offset, and increases * the position by the number of doubles read. * * @param dest the target double array. * @param off the offset of the double array, must not be negative and not greater than {@code dest.length}. * @param len the number of doubles to read, must be no less than zero and not greater than {@code dest.length - off}. * @return this buffer. * @exception IndexOutOfBoundsException if either {@code off} or {@code len} is invalid. * @exception BufferUnderflowException if {@code len} is greater than {@code remaining()}. * @since Android 1.0 */ public DoubleBuffer get(double[] dest, int off, int len) { int length = dest.length; if (off < 0 || len < 0 || (long) off + (long) len > length) { throw new IndexOutOfBoundsException(); } if (len > remaining()) { throw new BufferUnderflowException(); } for (int i = off; i < off + len; i++) { dest[i] = get(); } return this; } /** Returns a double at the specified index; the position is not changed. * * @param index the index, must not be negative and less than limit. * @return a double at the specified index. * @exception IndexOutOfBoundsException if index is invalid. * @since Android 1.0 */ public abstract double get(int index); /** Indicates whether this buffer is based on a double array and is read/write. * * @return {@code true} if this buffer is based on a double array and provides read/write access, {@code false} otherwise. * @since Android 1.0 */ public final boolean hasArray() { return protectedHasArray(); } // /** // * Calculates this buffer's hash code from the remaining chars. The // * position, limit, capacity and mark don't affect the hash code. // * // * @return the hash code calculated from the remaining chars. // * @since Android 1.0 // */ // public int hashCode() { // int myPosition = position; // int hash = 0; // long l; // while (myPosition < limit) { // l = Double.doubleToLongBits(get(myPosition++)); // hash = hash + ((int) l) ^ ((int) (l >> 32)); // } // return hash; // } /** Indicates whether this buffer is direct. A direct buffer will try its best to take advantage of native memory APIs and it * may not stay in the Java heap, so it is not affected by garbage collection. * <p> * A double buffer is direct if it is based on a byte buffer and the byte buffer is direct. * </p> * * @return {@code true} if this buffer is direct, {@code false} otherwise. * @since Android 1.0 */ public abstract boolean isDirect(); /** Returns the byte order used by this buffer when converting doubles from/to bytes. * <p> * If this buffer is not based on a byte buffer, then this always returns the platform's native byte order. * </p> * * @return the byte order used by this buffer when converting doubles from/to bytes. * @since Android 1.0 */ public abstract ByteOrder order(); /** Child class implements this method to realize {@code array()}. * * @see #array() */ abstract double[] protectedArray(); /** Child class implements this method to realize {@code arrayOffset()}. * * @see #arrayOffset() */ abstract int protectedArrayOffset(); /** Child class implements this method to realize {@code hasArray()}. * * @see #hasArray() */ abstract boolean protectedHasArray(); /** Writes the given double to the current position and increases the position by 1. * * @param d the double to write. * @return this buffer. * @exception BufferOverflowException if position is equal or greater than limit. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public abstract DoubleBuffer put(double d); /** Writes doubles from the given double array to the current position and increases the position by the number of doubles * written. * <p> * Calling this method has the same effect as {@code put(src, 0, src.length)}. * </p> * * @param src the source double array. * @return this buffer. * @exception BufferOverflowException if {@code remaining()} is less than {@code src.length}. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public final DoubleBuffer put(double[] src) { return put(src, 0, src.length); } /** Writes doubles from the given double array, starting from the specified offset, to the current position and increases the * position by the number of doubles written. * * @param src the source double array. * @param off the offset of double array, must not be negative and not greater than {@code src.length}. * @param len the number of doubles to write, must be no less than zero and not greater than {@code src.length - off}. * @return this buffer. * @exception BufferOverflowException if {@code remaining()} is less than {@code len}. * @exception IndexOutOfBoundsException if either {@code off} or {@code len} is invalid. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public DoubleBuffer put(double[] src, int off, int len) { int length = src.length; if (off < 0 || len < 0 || (long) off + (long) len > length) { throw new IndexOutOfBoundsException(); } if (len > remaining()) { throw new BufferOverflowException(); } for (int i = off; i < off + len; i++) { put(src[i]); } return this; } /** Writes all the remaining doubles of the {@code src} double buffer to this buffer's current position, and increases both * buffers' position by the number of doubles copied. * * @param src the source double buffer. * @return this buffer. * @exception BufferOverflowException if {@code src.remaining()} is greater than this buffer's {@code remaining()}. * @exception IllegalArgumentException if {@code src} is this buffer. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public DoubleBuffer put(DoubleBuffer src) { if (src == this) { throw new IllegalArgumentException(); } if (src.remaining() > remaining()) { throw new BufferOverflowException(); } double[] doubles = new double[src.remaining()]; src.get(doubles); put(doubles); return this; } /** Write a double to the specified index of this buffer and the position is not changed. * * @param index the index, must not be negative and less than the limit. * @param d the double to write. * @return this buffer. * @exception IndexOutOfBoundsException if index is invalid. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public abstract DoubleBuffer put(int index, double d); /** Returns a sliced buffer that shares its content with this buffer. * <p> * The sliced buffer's capacity will be this buffer's {@code remaining()}, and its zero position will correspond to this * buffer's current position. The new buffer's position will be 0, limit will be its capacity, and its mark is cleared. The new * buffer's read-only property and byte order are the same as this buffer's. * </p> * <p> * The new buffer shares its content with this buffer, which means either buffer's change of content will be visible to the * other. The two buffer's position, limit and mark are independent. * </p> * * @return a sliced buffer that shares its content with this buffer. * @since Android 1.0 */ public abstract DoubleBuffer slice(); /** Returns a string representing the state of this double buffer. * * @return A string representing the state of this double buffer. * @since Android 1.0 */ public String toString() { StringBuffer buf = new StringBuffer(); buf.append(getClass().getName()); buf.append(", status: capacity="); //$NON-NLS-1$ buf.append(capacity()); buf.append(" position="); //$NON-NLS-1$ buf.append(position()); buf.append(" limit="); //$NON-NLS-1$ buf.append(limit()); return buf.toString(); } }