int java.lang.
Object
.hashCode()
Returns a hash code value for the object. This method is supported for the benefit of hashtables such as those provided by java.util.Hashtable.
The general contract of hashCode is:
- Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals
- If two objects are equal according to the equals(Object) method, then calling the
hashCodemethod on each of the two objects must produce the same integer result. - It is not required that if two objects are unequal according to the
java.lang.Object.equals(java.lang.Object)method, then calling the hashCode
As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the JavaTM
a hash code value for this object. See Also: java.lang.Object.equals(java.lang.Object)
在每个改写了equals的类中，你必须也要改写hashCode方法，因为相等的对象必须具有相等的散列码hashCode。
例如：
类java.lang.String重写了equals方法，那么其hashCode方法也必须修改。
