Java IO.pdf - Nguyen Dang Binh

Java I/O
The getAttributes() method returns the attributes for this entry as documented in the
manifest file of the archive. In brief, an Attributes object is a map of the name/value pairs
for the entry. This will be discussed further in the next section. The getCertificates()
method returns an array of java.security. cert.Certificate objects formed from any
signature files for this entry stored in the archive. These can be used to allow some classes
more access to the system than they would normally get. I won't go into this possibility here;
the details are available in Java Security.
9.5.6 Attributes
The java.util.jar.Attributes class is mostly just a concrete implementation of the
java.util.Map interface from the Collections API.
public class Attributes implements Map, Cloneable // Java 2
An Attributes object is a container for an entry in a manifest file. Recall that the entry is
composed of name/value pairs; the keys of the map are the names, while the values of the
entries are the values of the map. The Attributes class is accessed almost entirely through
the methods of the Map interface and has three public constructors:
public Attributes() // Java 2
public Attributes(int size) // Java 2
public Attributes(Attributes a) // Java 2
However, these are primarily for Java's internal use. Most of the time, you'll simply retrieve
Attributes objects from the getAttributes() method of JarEntry or the
getAttributes() and getMainAttributes() method of Manifest.
The Attributes class implements all the usual Map methods:
public Object get(Object name) // Java 2
public Object put(Object name, Object value) // Java 2
public Object remove(Object name) // Java 2
public boolean containsValue(Object value) // Java 2
public boolean containsKey(Object name) // Java 2
public void putAll(Map attr) // Java 2
public void clear() // Java 2
public int size() // Java 2
public boolean isEmpty() // Java 2
public Set keySet() // Java 2
public Collection values() // Java 2
public Set entrySet() // Java 2
public boolean equals(Object o) // Java 2
public int hashCode() // Java 2
The key objects for this map should all be Attributes.Name objects. Attributes.Name is a
rare public inner class called Name inside the Attributes class. However, it's simplest to just
think of it as another class in java.util.jar with a somewhat funny name. This strangely
named class has a single constructor:
public Attributes.Name(String name) // Java 2
182