Java IO.pdf - Nguyen Dang Binh

Java I/O
Normally, the name argument is the name of the file that's being placed in the archive. It
should not be null, or a NullPointerException will be thrown. It is also required to be less
than 65,536 bytes long (which is plenty long for a filename). Java 2 adds one more public
constructor that copies the name, comment, modification time, CRC checksum, size,
compressed size, method, comment, and indeed everything except the actual data of the file
from an existing ZipEntry object. (It's unclear why you might need this.)
public ZipEntry(ZipEntry e) // Java 2
There are nine methods that return information about a specific entry in a zip file:
public String getName()
public long getTime()
public long getSize()
public long getCompressedSize()
public long getCrc()
public int getMethod()
public byte[] getExtra()
public String getComment()
public boolean isDirectory()
The name is simply the relative path and filename stored in the archive, like
sun/net/www/protocol/systemresource/ParseSystemURL.class or java/awt/Dialog.class. The
time is the last time this entry was modified. It is given as a long, counting the number of
milliseconds since midnight, January 1, 1970, Greenwich Mean Time. (This is not how the
time is stored in the zip file, but Java converts the time before returning it.) -1 indicates that
the modification time is not specified. The CRC is a 32-bit cyclic redundancy code for the
data that's used to determine whether or not the file is corrupt. If no CRC is included,
getCRC() returns -1.
The size is the original, uncompressed length of the data in bytes. The compressed size is the
length of the compressed data in bytes. The getSize() and getCompressedSize() methods
both return -1 to indicate that the size isn't known.
getMethod() tells you whether or not the data is compressed; it returns if the data is
uncompressed, 8 if it's compressed using the deflation format, and -1 if the compression
format is unknown. and 8 are given as the mnemonic constants ZipEntry.STORED and
ZipEntry.DEFLATED :
public static final int STORED = 0;
public static final int DEFLATED = 8;
Each entry may contain an arbitrary amount of extra data. If so, this data is returned in a byte
array by the getExtra() method. Similarly, each entry may contain an optional string
comment. If it does, the getComment() method returns it; if it doesn't, getComment() returns
null. Finally, the isDirectory() method returns true if the entry is a directory and false if
it isn't.
Example 9.9 is an improved ZipLister that prints information about the files in a zip archive.
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