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; import java.io.IOException; /** A buffer of chars. * <p> * A char buffer can be created in either one of the following ways: * </p> * <ul> * <li>{@link #allocate(int) Allocate} a new char array and create a buffer based on it;</li> * <li>{@link #wrap(char[]) Wrap} an existing char array to create a new buffer;</li> * <li>{@link #wrap(CharSequence) Wrap} an existing char sequence to create a new buffer;</li> * <li>Use {@link java.nio.ByteBuffer#asCharBuffer() ByteBuffer.asCharBuffer} to create a char buffer based on a byte buffer.</li> * </ul> * * @since Android 1.0 */ public abstract class CharBuffer extends Buffer implements Comparable<CharBuffer>, CharSequence, Appendable {// , Readable { /** Creates a char buffer based on a newly allocated char array. * * @param capacity the capacity of the new buffer. * @return the created char buffer. * @throws IllegalArgumentException if {@code capacity} is less than zero. * @since Android 1.0 */ public static CharBuffer allocate(int capacity) { if (capacity < 0) { throw new IllegalArgumentException(); } return BufferFactory.newCharBuffer(capacity); } /** Creates a new char buffer by wrapping the given char array. * <p> * Calling this method has the same effect as {@code wrap(array, 0, array.length)}. * </p> * * @param array the char array which the new buffer will be based on. * @return the created char buffer. * @since Android 1.0 */ public static CharBuffer wrap(char[] array) { return wrap(array, 0, array.length); } /** Creates a new char buffer by wrapping the given char 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 char 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 char buffer. * @exception IndexOutOfBoundsException if either {@code start} or {@code len} is invalid. * @since Android 1.0 */ public static CharBuffer wrap(char[] array, int start, int len) { int length = array.length; if ((start < 0) || (len < 0) || (long) start + (long) len > length) { throw new IndexOutOfBoundsException(); } CharBuffer buf = BufferFactory.newCharBuffer(array); buf.position = start; buf.limit = start + len; return buf; } /** Creates a new char buffer by wrapping the given char sequence. * <p> * Calling this method has the same effect as {@code wrap(chseq, 0, chseq.length())}. * </p> * * @param chseq the char sequence which the new buffer will be based on. * @return the created char buffer. * @since Android 1.0 */ public static CharBuffer wrap(CharSequence chseq) { return BufferFactory.newCharBuffer(chseq); } /** Creates a new char buffer by wrapping the given char sequence. * <p> * The new buffer's position will be {@code start}, limit will be {@code end}, capacity will be the length of the char sequence. * The new buffer is read-only. * </p> * * @param chseq the char sequence which the new buffer will be based on. * @param start the start index, must not be negative and not greater than {@code chseq.length()}. * @param end the end index, must be no less than {@code start} and no greater than {@code chseq.length()}. * @return the created char buffer. * @exception IndexOutOfBoundsException if either {@code start} or {@code end} is invalid. * @since Android 1.0 */ public static CharBuffer wrap(CharSequence chseq, int start, int end) { if (chseq == null) { throw new NullPointerException(); } if (start < 0 || end < start || end > chseq.length()) { throw new IndexOutOfBoundsException(); } CharBuffer result = BufferFactory.newCharBuffer(chseq); result.position = start; result.limit = end; return result; } /** Constructs a {@code CharBuffer} with given capacity. * * @param capacity the capacity of the buffer. * @since Android 1.0 */ CharBuffer(int capacity) { super(capacity); } /** Returns the char array which this buffer is based on, if there is one. * * @return the char 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 char[] array() { return protectedArray(); } /** Returns the offset of the char array which this buffer is based on, if there is one. * <p> * The offset is the index of the array corresponds to the zero position of the buffer. * </p> * * @return the offset of the char 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 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 CharBuffer asReadOnlyBuffer(); /** Returns the character located at the specified index in the buffer. The index value is referenced from the current buffer * position. * * @param index the index referenced from the current buffer position. It must not be less than zero but less than the value * obtained from a call to {@code remaining()}. * @return the character located at the specified index (referenced from the current position) in the buffer. * @exception IndexOutOfBoundsException if the index is invalid. * @since Android 1.0 */ public final char charAt(int index) { if (index < 0 || index >= remaining()) { throw new IndexOutOfBoundsException(); } return get(position + index); } /** Compacts this char buffer. * <p> * The remaining chars will be moved to the head of the buffer, starting 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 CharBuffer compact(); /** Compare the remaining chars of this buffer to another char buffer's remaining chars. * * @param otherBuffer another char buffer. * @return a negative value if this is less than {@code otherBuffer}; 0 if this equals to {@code otherBuffer}; a positive value * if this is greater than {@code otherBuffer}. * @exception ClassCastException if {@code otherBuffer} is not a char buffer. * @since Android 1.0 */ public int compareTo(CharBuffer otherBuffer) { int compareRemaining = (remaining() < otherBuffer.remaining()) ? remaining() : otherBuffer.remaining(); int thisPos = position; int otherPos = otherBuffer.position; char thisByte, otherByte; while (compareRemaining > 0) { thisByte = get(thisPos); otherByte = otherBuffer.get(otherPos); if (thisByte != otherByte) { return thisByte < otherByte ? -1 : 1; } thisPos++; otherPos++; compareRemaining--; } return remaining() - otherBuffer.remaining(); } /** Returns a duplicated buffer that shares its content with this buffer. * <p> * The duplicated buffer's initial 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 CharBuffer duplicate(); /** Checks whether this char buffer is equal to another object. * <p> * If {@code other} is not a char buffer then {@code false} is returned. Two char buffers are equal if and only if their * remaining chars are exactly the same. Position, limit, capacity and mark are not considered. * </p> * * @param other the object to compare with this char buffer. * @return {@code true} if this char buffer is equal to {@code other}, {@code false} otherwise. * @since Android 1.0 */ public boolean equals(Object other) { if (!(other instanceof CharBuffer)) { return false; } CharBuffer otherBuffer = (CharBuffer) 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 char at the current position and increases the position by 1. * * @return the char at the current position. * @exception BufferUnderflowException if the position is equal or greater than limit. * @since Android 1.0 */ public abstract char get(); /** Reads chars from the current position into the specified char array and increases the position by the number of chars read. * <p> * Calling this method has the same effect as {@code get(dest, 0, dest.length)}. * </p> * * @param dest the destination char array. * @return this buffer. * @exception BufferUnderflowException if {@code dest.length} is greater than {@code remaining()}. * @since Android 1.0 */ public CharBuffer get(char[] dest) { return get(dest, 0, dest.length); } /** Reads chars from the current position into the specified char array, starting from the specified offset, and increases the * position by the number of chars read. * * @param dest the target char array. * @param off the offset of the char array, must not be negative and not greater than {@code dest.length}. * @param len The number of chars to read, must be no less than zero and no 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 CharBuffer get(char[] 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 char at the specified index; the position is not changed. * * @param index the index, must not be negative and less than limit. * @return a char at the specified index. * @exception IndexOutOfBoundsException if index is invalid. * @since Android 1.0 */ public abstract char get(int index); /** Indicates whether this buffer is based on a char array and is read/write. * * @return {@code true} if this buffer is based on a byte 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; while (myPosition < limit) { hash = hash + get(myPosition++); } 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 char 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 number of remaining chars. * * @return the number of remaining chars. * @since Android 1.0 */ public final int length() { return remaining(); } /** Returns the byte order used by this buffer when converting chars 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 chars from/to bytes. * @since Android 1.0 */ public abstract ByteOrder order(); /** Child class implements this method to realize {@code array()}. * * @see #array() */ abstract char[] 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 char to the current position and increases the position by 1. * * @param c the char 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 CharBuffer put(char c); /** Writes chars from the given char array to the current position and increases the position by the number of chars written. * <p> * Calling this method has the same effect as {@code put(src, 0, src.length)}. * </p> * * @param src the source char 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 CharBuffer put(char[] src) { return put(src, 0, src.length); } /** Writes chars from the given char array, starting from the specified offset, to the current position and increases the * position by the number of chars written. * * @param src the source char array. * @param off the offset of char array, must not be negative and not greater than {@code src.length}. * @param len the number of chars to write, must be no less than zero and no 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 CharBuffer put(char[] 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 chars of the {@code src} char buffer to this buffer's current position, and increases both buffers' * position by the number of chars copied. * * @param src the source char 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 CharBuffer put(CharBuffer src) { if (src == this) { throw new IllegalArgumentException(); } if (src.remaining() > remaining()) { throw new BufferOverflowException(); } char[] contents = new char[src.remaining()]; src.get(contents); put(contents); return this; } /** Writes a char to the specified index of this buffer; the position is not changed. * * @param index the index, must be no less than zero and less than the limit. * @param c the char 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 CharBuffer put(int index, char c); /** Writes all chars of the given string to the current position of this buffer, and increases the position by the length of * string. * <p> * Calling this method has the same effect as {@code put(str, 0, str.length())}. * </p> * * @param str the string to write. * @return this buffer. * @exception BufferOverflowException if {@code remaining()} is less than the length of string. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public final CharBuffer put(String str) { return put(str, 0, str.length()); } /** Writes chars of the given string to the current position of this buffer, and increases the position by the number of chars * written. * * @param str the string to write. * @param start the first char to write, must not be negative and not greater than {@code str.length()}. * @param end the last char to write (excluding), must be less than {@code start} and not greater than {@code str.length()}. * @return this buffer. * @exception BufferOverflowException if {@code remaining()} is less than {@code end - start}. * @exception IndexOutOfBoundsException if either {@code start} or {@code end} is invalid. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public CharBuffer put(String str, int start, int end) { int length = str.length(); if (start < 0 || end < start || end > length) { throw new IndexOutOfBoundsException(); } if (end - start > remaining()) { throw new BufferOverflowException(); } for (int i = start; i < end; i++) { put(str.charAt(i)); } return this; } /** 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 same as this buffer. * </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 CharBuffer slice(); /** Returns a new char buffer representing a sub-sequence of this buffer's current remaining content. * <p> * The new buffer's position will be {@code position() + start}, limit will be {@code position() + end}, capacity will be the * same as this buffer. The new buffer's read-only property and byte order are the same as this buffer. * </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> * * @param start the start index of the sub-sequence, referenced from the current buffer position. Must not be less than zero * and not greater than the value obtained from a call to {@code remaining()}. * @param end the end index of the sub-sequence, referenced from the current buffer position. Must not be less than * {@code start} and not be greater than the value obtained from a call to {@code remaining()}. * @return a new char buffer represents a sub-sequence of this buffer's current remaining content. * @exception IndexOutOfBoundsException if either {@code start} or {@code end} is invalid. * @since Android 1.0 */ public abstract CharSequence subSequence(int start, int end); /** Returns a string representing the current remaining chars of this buffer. * * @return a string representing the current remaining chars of this buffer. * @since Android 1.0 */ public String toString() { StringBuffer strbuf = new StringBuffer(); for (int i = position; i < limit; i++) { strbuf.append(get(i)); } return strbuf.toString(); } /** Writes the given char to the current position and increases the position by 1. * * @param c the char 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 CharBuffer append(char c) { return put(c); } /** Writes all chars of the given character sequence {@code csq} to the current position of this buffer, and increases the * position by the length of the csq. * <p> * Calling this method has the same effect as {@code append(csq.toString())}. * </p> * If the {@code CharSequence} is {@code null} the string "null" will be written to the buffer. * * @param csq the {@code CharSequence} to write. * @return this buffer. * @exception BufferOverflowException if {@code remaining()} is less than the length of csq. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public CharBuffer append(CharSequence csq) { if (csq != null) { return put(csq.toString()); } return put("null"); //$NON-NLS-1$ } /** Writes chars of the given {@code CharSequence} to the current position of this buffer, and increases the position by the * number of chars written. * * @param csq the {@code CharSequence} to write. * @param start the first char to write, must not be negative and not greater than {@code csq.length()}. * @param end the last char to write (excluding), must be less than {@code start} and not greater than {@code csq.length()}. * @return this buffer. * @exception BufferOverflowException if {@code remaining()} is less than {@code end - start}. * @exception IndexOutOfBoundsException if either {@code start} or {@code end} is invalid. * @exception ReadOnlyBufferException if no changes may be made to the contents of this buffer. * @since Android 1.0 */ public CharBuffer append(CharSequence csq, int start, int end) { if (csq == null) { csq = "null"; //$NON-NLS-1$ } CharSequence cs = csq.subSequence(start, end); if (cs.length() > 0) { return put(cs.toString()); } return this; } /** Reads characters from this buffer and puts them into {@code target}. The number of chars that are copied is either the * number of remaining chars in this buffer or the number of remaining chars in {@code target}, whichever is smaller. * * @param target the target char buffer. * @throws IllegalArgumentException if {@code target} is this buffer. * @throws IOException if an I/O error occurs. * @throws ReadOnlyBufferException if no changes may be made to the contents of {@code target}. * @return the number of chars copied or -1 if there are no chars left to be read from this buffer. * @since Android 1.0 */ public int read(CharBuffer target) throws IOException { if (target == this) { throw new IllegalArgumentException(); } if (remaining() == 0) { return target.remaining() == 0 ? 0 : -1; } int result = Math.min(target.remaining(), remaining()); char[] chars = new char[result]; get(chars); target.put(chars); return result; } }