File	Doc	Category	Size	Date	Package
DataInputStream.java	API Doc	J2ME CLDC 1.1	19458	Wed Feb 05 15:55:58 GMT 2003	java.io

DataInputStream

• java.lang.Object
  • java.io.InputStream

Fields Summary
protected InputStream	in The input stream.

Constructors Summary
public DataInputStream(InputStream in) Creates a DataInputStream and saves its argument, the input stream in, for later use. param in the input stream. this.in = in;

Methods Summary
public int	available() Returns the number of bytes that can be read from this input stream without blocking. This method simply performs in.available() and returns the result. return the number of bytes that can be read from the input stream without blocking. exception IOException if an I/O error occurs. return in.available();
public void	close() Closes this input stream and releases any system resources associated with the stream. This method simply performs in.close(). exception IOException if an I/O error occurs. in.close();
public synchronized void	mark(int readlimit) Marks the current position in this input stream. A subsequent call to the reset method repositions this stream at the last marked position so that subsequent reads re-read the same bytes. The readlimit argument tells this input stream to allow that many bytes to be read before the mark position gets invalidated. This method simply performs in.mark(readlimit). param readlimit the maximum limit of bytes that can be read before the mark position becomes invalid. in.mark(readlimit);
public boolean	markSupported() Tests if this input stream supports the mark and reset methods. This method simply performs in.markSupported(). return true if this stream type supports the mark and reset method; false otherwise. return in.markSupported();
public int	read() Reads the next byte of data from this input stream. The value byte is returned as an int in the range 0 to 255. If no byte is available because the end of the stream has been reached, the value -1 is returned. This method blocks until input data is available, the end of the stream is detected, or an exception is thrown. This method simply performs in.read() and returns the result. return the next byte of data, or -1 if the end of the stream is reached. exception IOException if an I/O error occurs. return in.read();
public final int	read(byte[] b) See the general contract of the read method of DataInput. Bytes for this operation are read from the contained input stream. param b the buffer into which the data is read. return the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached. exception IOException if an I/O error occurs. see java.io.InputStream#read(byte[], int, int) return in.read(b, 0, b.length);
public final int	read(byte[] b, int off, int len) Reads up to len bytes of data from this input stream into an array of bytes. This method blocks until some input is available. This method simply performs in.read(b, off, len) and returns the result. param b the buffer into which the data is read. param off the start offset of the data. param len the maximum number of bytes read. return the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached. exception IOException if an I/O error occurs. return in.read(b, off, len);
public final boolean	readBoolean() See the general contract of the readBoolean method of DataInput. Bytes for this operation are read from the contained input stream. return the boolean value read. exception EOFException if this input stream has reached the end. exception IOException if an I/O error occurs. int ch = read(); if (ch < 0) { throw new EOFException(); } return (ch != 0);
public final byte	readByte() See the general contract of the readByte method of DataInput. Bytes for this operation are read from the contained input stream. return the next byte of this input stream as a signed 8-bit byte. exception EOFException if this input stream has reached the end. exception IOException if an I/O error occurs. int ch = read(); if (ch < 0) { throw new EOFException(); } return (byte)(ch);
public final char	readChar() See the general contract of the readChar method of DataInput. Bytes for this operation are read from the contained input stream. return the next two bytes of this input stream as a Unicode character. exception EOFException if this input stream reaches the end before reading two bytes. exception IOException if an I/O error occurs. return (char)readUnsignedShort();
public final double	readDouble() See the general contract of the readDouble method of DataInput. Bytes for this operation are read from the contained input stream. return the next eight bytes of this input stream, interpreted as a double. exception EOFException if this input stream reaches the end before reading eight bytes. exception IOException if an I/O error occurs. see java.io.DataInputStream#readLong() see java.lang.Double#longBitsToDouble(long) since CLDC 1.1 return Double.longBitsToDouble(readLong());
public final float	readFloat() See the general contract of the readFloat method of DataInput. Bytes for this operation are read from the contained input stream. return the next four bytes of this input stream, interpreted as a float. exception EOFException if this input stream reaches the end before reading four bytes. exception IOException if an I/O error occurs. see java.io.DataInputStream#readInt() see java.lang.Float#intBitsToFloat(int) since CLDC 1.1 return Float.intBitsToFloat(readInt());
public final void	readFully(byte[] b) See the general contract of the readFully method of DataInput. Bytes for this operation are read from the contained input stream. param b the buffer into which the data is read. exception EOFException if this input stream reaches the end before reading all the bytes. exception IOException if an I/O error occurs. readFully(b, 0, b.length);
public final void	readFully(byte[] b, int off, int len) See the general contract of the readFully method of DataInput. Bytes for this operation are read from the contained input stream. param b the buffer into which the data is read. param off the start offset of the data. param len the number of bytes to read. exception EOFException if this input stream reaches the end before reading all the bytes. exception IOException if an I/O error occurs. if (len < 0) { throw new IndexOutOfBoundsException(); } int n = 0; while (n < len) { int count = read(b, off + n, len - n); if (count < 0) { throw new EOFException(); } n += count; }
public final int	readInt() See the general contract of the readInt method of DataInput. Bytes for this operation are read from the contained input stream. return the next four bytes of this input stream, interpreted as an int. exception EOFException if this input stream reaches the end before reading four bytes. exception IOException if an I/O error occurs. int ch1 = read(); int ch2 = read(); int ch3 = read(); int ch4 = read(); if ((ch1 | ch2 | ch3 | ch4) < 0) { throw new EOFException(); } return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
public final long	readLong() See the general contract of the readLong method of DataInput. Bytes for this operation are read from the contained input stream. return the next eight bytes of this input stream, interpreted as a long. exception EOFException if this input stream reaches the end before reading eight bytes. exception IOException if an I/O error occurs. return ((long)(readInt()) << 32) + (readInt() & 0xFFFFFFFFL);
public final short	readShort() See the general contract of the readShort method of DataInput. Bytes for this operation are read from the contained input stream. return the next two bytes of this input stream, interpreted as a signed 16-bit number. exception EOFException if this input stream reaches the end before reading two bytes. exception IOException if an I/O error occurs. return (short)readUnsignedShort();
public final java.lang.String	readUTF() See the general contract of the readUTF method of DataInput. Bytes for this operation are read from the contained input stream. return a Unicode string. exception EOFException if this input stream reaches the end before reading all the bytes. exception IOException if an I/O error occurs. see java.io.DataInputStream#readUTF(java.io.DataInput) return readUTF(this);
public static final java.lang.String	readUTF(java.io.DataInput in) Reads from the stream in a representation of a Unicode character string encoded in Java modified UTF-8 format; this string of characters is then returned as a String. The details of the modified UTF-8 representation are exactly the same as for the readUTF method of DataInput. param in a data input stream. return a Unicode string. exception EOFException if the input stream reaches the end before all the bytes. exception IOException if an I/O error occurs. exception UTFDataFormatException if the bytes do not represent a valid UTF-8 encoding of a Unicode string. see java.io.DataInputStream#readUnsignedShort() int utflen = in.readUnsignedShort(); char str[] = new char[utflen]; byte bytearr [] = new byte[utflen]; int c, char2, char3; int count = 0; int strlen = 0; in.readFully(bytearr, 0, utflen); while (count < utflen) { c = (int) bytearr[count] & 0xff; switch (c >> 4) { case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: /* 0xxxxxxx*/ count++; str[strlen++] = (char)c; break; case 12: case 13: /* 110x xxxx 10xx xxxx*/ count += 2; if (count > utflen) throw new UTFDataFormatException(); char2 = (int) bytearr[count-1]; if ((char2 & 0xC0) != 0x80) throw new UTFDataFormatException(); str[strlen++] = (char)(((c & 0x1F) << 6) | (char2 & 0x3F)); break; case 14: /* 1110 xxxx 10xx xxxx 10xx xxxx */ count += 3; if (count > utflen) throw new UTFDataFormatException(); char2 = (int) bytearr[count-2]; char3 = (int) bytearr[count-1]; if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80)) throw new UTFDataFormatException(); str[strlen++] = (char)(((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0)); break; default: /* 10xx xxxx, 1111 xxxx */ throw new UTFDataFormatException(); } } // The number of chars produced may be less than utflen return new String(str, 0, strlen);
public final int	readUnsignedByte() See the general contract of the readUnsignedByte method of DataInput. Bytes for this operation are read from the contained input stream. return the next byte of this input stream, interpreted as an unsigned 8-bit number. exception EOFException if this input stream has reached the end. exception IOException if an I/O error occurs. int ch = read(); if (ch < 0) { throw new EOFException(); } return ch;
public final int	readUnsignedShort() See the general contract of the readUnsignedShort method of DataInput. Bytes for this operation are read from the contained input stream. return the next two bytes of this input stream, interpreted as an unsigned 16-bit integer. exception EOFException if this input stream reaches the end before reading two bytes. exception IOException if an I/O error occurs. int ch1 = read(); int ch2 = read(); if ((ch1 | ch2) < 0) { throw new EOFException(); } return (ch1 << 8) + (ch2 << 0);
public synchronized void	reset() Repositions this stream to the position at the time the mark method was last called on this input stream. This method simply performs in.reset(). Stream marks are intended to be used in situations where you need to read ahead a little to see what's in the stream. Often this is most easily done by invoking some general parser. If the stream is of the type handled by the parse, it just chugs along happily. If the stream is not of that type, the parser should toss an exception when it fails. If this happens within readlimit bytes, it allows the outer code to reset the stream and try another parser. exception IOException if the stream has not been marked or if the mark has been invalidated. in.reset();
public long	skip(long n) Skips over and discards n bytes of data from the input stream. The skip method may, for a variety of reasons, end up skipping over some smaller number of bytes, possibly 0. The actual number of bytes skipped is returned. This method simply performs in.skip(n). param n the number of bytes to be skipped. return the actual number of bytes skipped. exception IOException if an I/O error occurs. return in.skip(n);
public final int	skipBytes(int n) See the general contract of the skipBytes method of DataInput. Bytes for this operation are read from the contained input stream. param n the number of bytes to be skipped. return the actual number of bytes skipped. exception IOException if an I/O error occurs. int total = 0; int cur = 0; while ((total<n) && ((cur = (int) skip(n-total)) > 0)) { total += cur; } return total;