Java 中的CharArrayReader 介绍_动力节点Java学院整理

CharArrayReader(char[] buf)CharArrayReader(char[] buf, int offset, int length)void   close()void   mark(int readLimit)boolean  markSupported()int    read()int    read(char[] buffer, int offset, int len)boolean  ready()void   reset()long   skip(long charCount)

 package java.io; public abstract class Reader implements Readable, Closeable {   protected Object lock;   protected Reader() {     this.lock = this;   }   protected Reader(Object lock) {     if (lock == null) {       throw new NullPointerException();     }     this.lock = lock;   }   public int read(java.nio.CharBuffer target) throws IOException {     int len = target.remaining();     char[] cbuf = new char[len];     int n = read(cbuf, 0, len);     if (n > 0)       target.put(cbuf, 0, n);     return n;   }   public int read() throws IOException {    char cb[] = new char[1];     if (read(cb, 0, 1) == -1)       return -1;     else       return cb[0];   }   public int read(char cbuf[]) throws IOException {     return read(cbuf, 0, cbuf.length);   }   abstract public int read(char cbuf[], int off, int len) throws IOException;   private static final int maxSkipBufferSize = 8192;   private char skipBuffer[] = null;   public long skip(long n) throws IOException {     if (n < L)       throw new IllegalArgumentException("skip value is negative");     int nn = (int) Math.min(n, maxSkipBufferSize);     synchronized (lock) {       if ((skipBuffer == null) || (skipBuffer.length < nn))       while (r > 0) {        int nc = read(skipBuffer, 0, (int)Math.min(r, nn));        if (nc == -1)           break;         r -= nc;       }       return n - r;     }   }   public boolean ready() throws IOException {     return false;   }   public boolean markSupported() {     return false;   }   public void mark(int readAheadLimit) throws IOException {     throw new IOException("mark() not supported");   }   public void reset() throws IOException {     throw new IOException("reset() not supported");   }   abstract public void close() throws IOException; }

  package java.io;  public class CharArrayReader extends Reader {    // 字符数组缓冲    protected char buf[];    // 下一个被获取的字符的位置    protected int pos;   // 被标记的位置   protected int markedPos = 0;   // 字符缓冲的长度   protected int count;   // 构造函数   public CharArrayReader(char buf[]) {     this.buf = buf;     this.pos = 0;     this.count = buf.length;   }   // 构造函数     if ((offset < 0) || (offset > buf.length) || (length < 0) ||      ((offset + length) < 0)) {       throw new IllegalArgumentException();     }     this.buf = buf;     this.pos = offset;     this.count = Math.min(offset + length, buf.length);     this.markedPos = offset;   }   // 判断“CharArrayReader是否有效”。   // 若字符缓冲为null，则认为其无效。   private void ensureOpen() throws IOException {     if (buf == null)       throw new IOException("Stream closed");   }   // 读取下一个字符。即返回字符缓冲区中下一位置的值。   // 注意：读取的是字符！   public int read() throws IOException {     synchronized (lock) {       ensureOpen();       if (pos >= count)         return -1;       else         return buf[pos++];     }   }   // 读取数据，并保存到字符数组b中从off开始的位置中，len是读取长度。   public int read(char b[], int off, int len) throws IOException {     synchronized (lock) {       ensureOpen();       if ((off < 0) || (off > b.length) || (len < 0) ||         ((off + len) > b.length) || ((off + len) < 0)) {         throw new IndexOutOfBoundsException();       } else if (len == 0) {         return 0;       }       if (pos >= count) {         return -;       }       if (pos + len > count) {         len = count - pos;       }      if (len <= 0) {        return 0;       }       System.arraycopy(buf, pos, b, off, len);       pos += len;       return len;     }   }   // 跳过n个字符   public long skip(long n) throws IOException {     synchronized (lock) {       ensureOpen();       if (pos + n > count) {         n = count - pos;       }       if (n < 0) {         return 0;       }       pos += n;       return n;     }   }   // 判断“是否能读取下一个字符”。能的话，返回true。   public boolean ready() throws IOException {     synchronized (lock) {       ensureOpen();       return (count - pos) > ;     }   }   public boolean markSupported() {     return true;   }   // 保存当前位置。readAheadLimit在此处没有任何实际意义   // mark()必须和reset()配合使用才有意义！   public void mark(int readAheadLimit) throws IOException {     synchronized (lock) {       ensureOpen();       markedPos = pos;     }   }   // 重置“下一个读取位置”为“mark所标记的位置”   public void reset() throws IOException {     synchronized (lock) {       ensureOpen();       pos = markedPos;     }   }   public void close() {     buf = null;   } }

 /**  * CharArrayReader 演示程序  *  *   */ import java.io.CharArrayReader; import java.io.CharArrayWriter; import java.io.IOException; public class CharArrayReaderTest {   private static final int LEN = 5;   // 对应英文字母“abcdefghijklmnopqrstuvwxyz”   private static final char[] ArrayLetters = new char[] {'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};   public static void main(String[] args) {     tesCharArrayReader() ;   }   /**   * CharArrayReader的API测试函数   */   private static void tesCharArrayReader() {     try {       // 创建CharArrayReader字符流，内容是ArrayLetters数组       CharArrayReader car = new CharArrayReader(ArrayLetters);      // 从字符数组流中读取5个字符       for (int i=; i<LEN; i++) {         // 若能继续读取下一个字符，则读取下一个字符         if (car.ready() == true) {           // 读取“字符流的下一个字符”           char tmp = (char)car.read();           System.out.printf("%d : %c/n", i, tmp);         }       }       // 若“该字符流”不支持标记功能，则直接退出       if (!car.markSupported()) {         System.out.println("make not supported!");         return ;       }      // 标记“字符流中下一个被读取的位置”。即--标记“f”，因为因为前面已经读取了5个字符，所以下一个被读取的位置是第6个字符”      // (01), CharArrayReader类的mark(0)函数中的“参数0”是没有实际意义的。      // (02), mark()与reset()是配套的，reset()会将“字符流中下一个被读取的位置”重置为“mark()中所保存的位置”      car.mark(0);      // 跳过5个字符。跳过5个字符后，字符流中下一个被读取的值应该是“k”。       car.skip(5);       // 从字符流中读取个数据。即读取“klmno”       char[] buf = new char[LEN];      car.read(buf, 0, LEN);       System.out.printf("buf=%s/n", String.valueOf(buf));       // 重置“字符流”：即，将“字符流中下一个被读取的位置”重置到“mark()所标记的位置”，即f。       car.reset();       // 从“重置后的字符流”中读取5个字符到buf中。即读取“fghij”      car.read(buf, 0, LEN);       System.out.printf("buf=%s/n", String.valueOf(buf));     } catch (IOException e) {       e.printStackTrace();     }   } }

0 : a1 : b2 : c3 : d4 : ebuf=klmnobuf=fghij