java hashcode and equals contract

) = true I = i2 = true I1.equals (I) = true I = i4 = true I4.equals (I) = true 3> hashcode and equals of the object1) to understand the role of hashcode, we can understand it in java. lang. Object. Every time a new JVM Object is

The following is an official document definition for hashcode:[Plain]View Plaincopy The Hashcode method returns the hash code value of the object. This method is supported to provide some advantages to the hash table, for example, the Hashtable provided by Java.util.Hashtable. The general agreement of Hashcode is: During

Java Basics (1) hashcode ()See an article about Hashcode (), written in a very detailed understanding, a sudden feeling of an epiphany, so specifically turned around. Original:http://blog.csdn.net/fenglibing/article/details/8905007Reference:http://www.importnew.com/11334.htmlThe following is an official document definition for hashcode:The

comparison reference is the same).Hashcode () is a local method, and its implementation is dependent on the local machine.2. The Java language requirements for Equals () are as follows, and these requirements must be followed:A symmetry: If X.equals (y) returns "true", then Y.equals (x) should also return "true".B reflectivity: x.equals (x) must return is "true"

Introduction to the hashcode method in Java The hash table data structure is certainly not unfamiliar to most people, and hash tables are used in many places to improve the search efficiency. There is a method in the Object class of Java: public native int hashCode(); According to the declaration of this method, this m

Hash table This data structure presumably most people are not unfamiliar, and in many places will use hash tables to improve the search efficiency. There is a method in the object class in Java:public native int hashcode ();According to the declaration of this method, the method returns a numeric value of type int and is a local method, so no specific implementation is given in the object class.Why does the object class need such a method? What role d

On the Hashcode method in Java Hash table This data structure presumably most people are not unfamiliar, and in many places will use hash tables to improve the search efficiency. There is a method in the object class in Java: public native int hashcode (); Why does the object class need such a method? What role does it

The following is an official document definition for hashcode: The Hashcode method returns the hash code value of the object.This method is supported to provide some advantages to the hash table, for example, the Hashtable provided by Java.util.Hashtable. The general contract for Hashcode is that during

A hash table This data structure must be familiar to most people, and in many places, hash tables are used to improve search efficiency. There is a method in the Java object class: According to the declaration of this method, the method returns a numeric value of type int and is a local method, so no specific implementation is given in the object class. Why does the object class need such a method? How does it work? Today we will discus

into the collection, how do you determine if the object already exists in the collection? Perhaps most people would have thought of calling the Equals method to make comparisons on a case by case basis. However, if there are already 10,000 or more data in the collection, if the Equals method is used to compare each other, efficiency must be a problem. At this point the function of the

First, to understand the role of hashcode, you must first know the collection in Java.In general, there are two types of collections (Collection) in Java, one is list, and the other is set. Do you know the difference between them? The elements within the set are ordered, the elements can be repeated, the latter elements are unordered, but the elements are not repeatable. So here is a more serious problem: t

First, why should have hash algorithmThere are two types of collections in Java , one is list, and the other is set. The elements in the list are ordered and the elements can be duplicated. The set element is unordered, but the element is not repeatable. If you want to ensure that the elements are not duplicated, should the two elements be repeated according to what to judge? Use the Object.Equals method. However, if each additional element is checked

First look at the object source code in the Hashcode method: /*** Returns A hash code value for the object. This method is* Supported for the benefit of hashtables such as those provided by* * * The general contract of * * * An execution of a Java application, the * must consistently return the same integer, provided no information* used in * This integer need no

HashCode (); It is a local method, and its implementation is related to the local machine. Here we temporarily think that the physical location of the Object Storage is returned (actually not, it is easy to understand here ). When we add an element to a set, the set will first call the hashCode method, so that we can directly locate the location it stores. If there are no other elements, it will be saved di

The following is an official definition of hashcode document: The hashcode method returns the hash code value of this object. This method provides some advantages for the hash table, such as the hash table provided by Java. util. hashtable. The conventional hashcode protocol is that, when calling the

Equals (object obj) method to be true. Simply put: "If two objects are the same, their hashcode should be equal". But note: This is just a spec, and if you're writing a class so that equals (Object obj) returns True and Hashcode () returns two unequal values, compile and run without error. This violates the

) =" + (i1.equals (i))); System.out.println (); System.out.println ("i = = I4 =" + (i = = i4)); System.out.println ("i4.equals (i) =" + (i4.equals (i))); ------------------------------ I1 = = I2 = true I1.equals (I2) = true i3 = = I4 = false I3.equals (