clime.messadmin.utils.SimpleEntry Maven / Gradle / Ivy
/**
*
*/
package clime.messadmin.utils;
import java.io.Serializable;
import java.util.Map;
/**
* An Entry maintaining a key and a value. The value may be
* changed using the setValue method. This class
* facilitates the process of building custom map
* implementations. For example, it may be convenient to return
* arrays of SimpleEntry instances in method
* Map.entrySet().toArray.
*
* @author Cédrik LIME
*/
public class SimpleEntry implements Map.Entry, Serializable {
private final Object key;
private Object value;
/**
* Creates an entry representing a mapping from the specified
* key to the specified value.
*
* @param key the key represented by this entry
* @param value the value represented by this entry
*/
public SimpleEntry(Object key, Object value) {
this.key = key;
this.value = value;
}
/**
* Creates an entry representing the same mapping as the
* specified entry.
*
* @param entry the entry to copy
*/
public SimpleEntry(Map.Entry entry) {
this.key = entry.getKey();
this.value = entry.getValue();
}
/**
* @return the key corresponding to this entry
*/
public Object getKey() {
return key;
}
/**
* @return the value corresponding to this entry
*/
public Object getValue() {
return value;
}
/**
* Replaces the value corresponding to this entry with the specified
* value.
*
* @param value new value to be stored in this entry
* @return the old value corresponding to the entry
*/
public Object setValue(Object value) {
Object oldValue = this.value;
this.value = value;
return oldValue;
}
/**
* Compares the specified object with this entry for equality.
* Returns {@code true} if the given object is also a map entry and
* the two entries represent the same mapping. More formally, two
* entries {@code e1} and {@code e2} represent the same mapping
* if
* (e1.getKey()==null ?
* e2.getKey()==null :
* e1.getKey().equals(e2.getKey()))
* &&
* (e1.getValue()==null ?
* e2.getValue()==null :
* e1.getValue().equals(e2.getValue()))
* This ensures that the {@code equals} method works properly across
* different implementations of the {@code Map.Entry} interface.
*
* @param o object to be compared for equality with this map entry
* @return {@code true} if the specified object is equal to this map
* entry
* @see #hashCode
*/
public boolean equals(Object o) {
if (!(o instanceof Map.Entry))
return false;
Map.Entry e = (Map.Entry)o;
return eq(key, e.getKey()) && eq(value, e.getValue());
}
/**
* Returns the hash code value for this map entry. The hash code
* of a map entry {@code e} is defined to be:
* (e.getKey()==null ? 0 : e.getKey().hashCode()) ^
* (e.getValue()==null ? 0 : e.getValue().hashCode())
* This ensures that {@code e1.equals(e2)} implies that
* {@code e1.hashCode()==e2.hashCode()} for any two Entries
* {@code e1} and {@code e2}, as required by the general
* contract of {@link Object#hashCode}.
*
* @return the hash code value for this map entry
* @see #equals
*/
public int hashCode() {
return (key == null ? 0 : key.hashCode()) ^
(value == null ? 0 : value.hashCode());
}
/**
* Returns a String representation of this map entry. This
* implementation returns the string representation of this
* entry's key followed by the equals character ("=")
* followed by the string representation of this entry's value.
*
* @return a String representation of this map entry
*/
public String toString() {
return key + "=" + value;
}
/**
* Utility method for SimpleEntry and SimpleImmutableEntry.
* Test for equality, checking for nulls.
*/
private static boolean eq(Object o1, Object o2) {
return o1 == null ? o2 == null : o1.equals(o2);
}
}