File	Doc	Category	Size	Date	Package
DataInputStream.java	API Doc	Java SE 5 API	22804	Fri Aug 26 14:56:58 BST 2005	java.io

DataInputStream

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

Fields Summary
private byte[]	bytearr working arrays initialized on demand by readUTF
private char[]	chararr
private byte[]	readBuffer
private char[]	lineBuffer

Constructors Summary
public DataInputStream(InputStream in) Creates a DataInputStream that uses the specified underlying InputStream. param in the specified input stream super(in);

Methods Summary
public final int	read(byte[] b) Reads some number of bytes from the contained input stream and stores them into the buffer array b. The number of bytes actually read is returned as an integer. This method blocks until input data is available, end of file is detected, or an exception is thrown. If b is null, a NullPointerException is thrown. If the length of b is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b. The first byte read is stored into element b[0], the next one into b[1], and so on. The number of bytes read is, at most, equal to the length of b. Let k be the number of bytes actually read; these bytes will be stored in elements b[0] through b[k-1], leaving elements b[k] through b[b.length-1] unaffected. If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed. The read(b) method has the same effect as: read(b, 0, b.length) 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.FilterInputStream#in 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 the contained input stream into an array of bytes. An attempt is made to read as many as len bytes, but a smaller number may be read, possibly zero. The number of bytes actually read is returned as an integer. This method blocks until input data is available, end of file is detected, or an exception is thrown. If b is null, a NullPointerException is thrown. If off is negative, or len is negative, or off+len is greater than the length of the array b, then an IndexOutOfBoundsException is thrown. If len is zero, then no bytes are read and 0 is returned; otherwise, there is an attempt to read at least one byte. If no byte is available because the stream is at end of file, the value -1 is returned; otherwise, at least one byte is read and stored into b. The first byte read is stored into element b[off], the next one into b[off+1], and so on. The number of bytes read is, at most, equal to len. Let k be the number of bytes actually read; these bytes will be stored in elements b[off] through b[off+k-1], leaving elements b[off+k] through b[off+len-1] unaffected. In every case, elements b[0] through b[off] and elements b[off+len] through b[b.length-1] are unaffected. If the first byte cannot be read for any reason other than end of file, then an IOException is thrown. In particular, an IOException is thrown if the input stream has been closed. 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. see java.io.FilterInputStream#in see java.io.InputStream#read(byte[], int, int) 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. see java.io.FilterInputStream#in int ch = in.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. see java.io.FilterInputStream#in int ch = in.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. see java.io.FilterInputStream#in int ch1 = in.read(); int ch2 = in.read(); if ((ch1 | ch2) < 0) throw new EOFException(); return (char)((ch1 << 8) + (ch2 << 0));
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) 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) 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. see java.io.FilterInputStream#in 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. see java.io.FilterInputStream#in if (len < 0) throw new IndexOutOfBoundsException(); int n = 0; while (n < len) { int count = in.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. see java.io.FilterInputStream#in int ch1 = in.read(); int ch2 = in.read(); int ch3 = in.read(); int ch4 = in.read(); if ((ch1 | ch2 | ch3 | ch4) < 0) throw new EOFException(); return ((ch1 << 24) + (ch2 << 16) + (ch3 << 8) + (ch4 << 0));
public final java.lang.String	readLine() See the general contract of the readLine method of DataInput. Bytes for this operation are read from the contained input stream. deprecated This method does not properly convert bytes to characters. As of JDK 1.1, the preferred way to read lines of text is via the BufferedReader.readLine() method. Programs that use the DataInputStream class to read lines can be converted to use the BufferedReader class by replacing code of the form: DataInputStream d = new DataInputStream(in); with: BufferedReader d = new BufferedReader(new InputStreamReader(in)); return the next line of text from this input stream. exception IOException if an I/O error occurs. see java.io.BufferedReader#readLine() see java.io.FilterInputStream#in char buf[] = lineBuffer; if (buf == null) { buf = lineBuffer = new char[128]; } int room = buf.length; int offset = 0; int c; loop: while (true) { switch (c = in.read()) { case -1: case '\n": break loop; case '\r": int c2 = in.read(); if ((c2 != '\n") && (c2 != -1)) { if (!(in instanceof PushbackInputStream)) { this.in = new PushbackInputStream(in); } ((PushbackInputStream)in).unread(c2); } break loop; default: if (--room < 0) { buf = new char[offset + 128]; room = buf.length - offset - 1; System.arraycopy(lineBuffer, 0, buf, 0, offset); lineBuffer = buf; } buf[offset++] = (char) c; break; } } if ((c == -1) && (offset == 0)) { return null; } return String.copyValueOf(buf, 0, offset);
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. see java.io.FilterInputStream#in readFully(readBuffer, 0, 8); return (((long)readBuffer[0] << 56) + ((long)(readBuffer[1] & 255) << 48) + ((long)(readBuffer[2] & 255) << 40) + ((long)(readBuffer[3] & 255) << 32) + ((long)(readBuffer[4] & 255) << 24) + ((readBuffer[5] & 255) << 16) + ((readBuffer[6] & 255) << 8) + ((readBuffer[7] & 255) << 0));
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. see java.io.FilterInputStream#in int ch1 = in.read(); int ch2 = in.read(); if ((ch1 | ch2) < 0) throw new EOFException(); return (short)((ch1 << 8) + (ch2 << 0));
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. exception UTFDataFormatException if the bytes do not represent a valid modified UTF-8 encoding of a string. 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 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 modified UTF-8 encoding of a Unicode string. see java.io.DataInputStream#readUnsignedShort() int utflen = in.readUnsignedShort(); byte[] bytearr = null; char[] chararr = null; if (in instanceof DataInputStream) { DataInputStream dis = (DataInputStream)in; if (dis.bytearr.length < utflen){ dis.bytearr = new byte[utflen*2]; dis.chararr = new char[utflen*2]; } chararr = dis.chararr; bytearr = dis.bytearr; } else { bytearr = new byte[utflen]; chararr = new char[utflen]; } int c, char2, char3; int count = 0; int chararr_count=0; in.readFully(bytearr, 0, utflen); while (count < utflen) { c = (int) bytearr[count] & 0xff; if (c > 127) break; count++; chararr[chararr_count++]=(char)c; } 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++; chararr[chararr_count++]=(char)c; break; case 12: case 13: /* 110x xxxx 10xx xxxx*/ count += 2; if (count > utflen) throw new UTFDataFormatException( "malformed input: partial character at end"); char2 = (int) bytearr[count-1]; if ((char2 & 0xC0) != 0x80) throw new UTFDataFormatException( "malformed input around byte " + count); chararr[chararr_count++]=(char)(((c & 0x1F) << 6) | (char2 & 0x3F)); break; case 14: /* 1110 xxxx 10xx xxxx 10xx xxxx */ count += 3; if (count > utflen) throw new UTFDataFormatException( "malformed input: partial character at end"); char2 = (int) bytearr[count-2]; char3 = (int) bytearr[count-1]; if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80)) throw new UTFDataFormatException( "malformed input around byte " + (count-1)); chararr[chararr_count++]=(char)(((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0)); break; default: /* 10xx xxxx, 1111 xxxx */ throw new UTFDataFormatException( "malformed input around byte " + count); } } // The number of chars produced may be less than utflen return new String(chararr, 0, chararr_count);
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. see java.io.FilterInputStream#in int ch = in.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. see java.io.FilterInputStream#in int ch1 = in.read(); int ch2 = in.read(); if ((ch1 | ch2) < 0) throw new EOFException(); return (ch1 << 8) + (ch2 << 0);
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) in.skip(n-total)) > 0)) { total += cur; } return total;