equals and hashcode java 8

Value) is returned ). If we want to get the expected results, we need to rewrite the toString method. [Java]Package mark. demo;Public class EnumDemo {Public static void main (String [] args ){For (Color color: Color. values ()){System. out. println (color );}}Public enum Color {RED ("red color", 0), GREEN ("green color", 1), BLUE ("blue color", 2), YELLOW ("Yellow color", 3 );Color (String name, int id ){_ Name = name;_ Id = id;}Private String _ name

　　Equals in object is used to compare the equality of two objects, in general, when overriding this method, it is often necessary to also rewrite hashcode to maintain the general contract of the Hashcode method, which declares that the equality object must have an equal hash code. That is: if Obj1.equals (OBJ2) is true

same.Rewrite the sample code for Hashcode: public int hashcode () {SOP (THIS.name + "... hashcode");return This.name.hashCode () + 29*age;} Thirdly, what is the mechanism of ArrayList?[1]. HashSet judgment, deletion, and addition of elements are based on the hashcode () and

I need to record some of the things I saw in Sunday, or I'll forget about them.Hashcode, equals:1) Each Java object has the Hashcode and equals methods.The ultimate Java class is the object class, so how does the object class label itself, that is, how the class of object di

In Java, equals and hashcode have design requirements, equals equal, then hashcode must be equal, or vice versa. Why is there such a requirement? In the collection, such as HashSet, the object required to be placed can not be repeated, how to determine it? The

When learning Java basic data types and complex data types, especially equals () "= =" and the Hashcode () part, not very understand, also stayed a long time, finally a bit of a look.To understand equals () "= =" and Hashcode (), it's a good idea to first understand the heap

Download Java interview book:Http://download.csdn.net/source/3563084 Set and list are two sub-interfaces of collection. The elements in set must be unique. Therefore, the equals method must be rewritten. For the hashset method, the hashcode method must be rewritten. When an element is added to a hahset, It is not added to determine whether the element already ex

1.equals () In the beginner Java, many people will say that when comparing objects, = = is the comparison of the address, equals () is the content of the comparison object, who said? Look at the definition of the Equals () method in the object class: public　boolean　equals

There are three methods in the object class in Java that have hashcode (), Equals (), and toString (), so there are three methods in all the classes in Java.In the object class the implementation of the ToString () method is the address of the printed object, which is printed out of the human can not understand, this information is not useful to print out. So in

("") ; //System.out.println ("HashMap object hashcode:" + mi.hashcode ());Hm.put (HM, "XX") ; //get a value from HashMap using the Get method of HashMap /** 1. Calculate its hash value according to the object passed in, and find the corresponding array position. * 2. The Equals method is used to determine whether the value on the array position is equal to the value. * 3. Equal retur

Doubleadouble;PrivateUnit Aobject;Private int[] ints;PrivateUnit[] Units; Public BooleanEquals (Object o) {if(! (OinstanceofUnit))return false; Unit unit = (unit) o;returnUnit.ashort = = Ashort Unit.achar = = Achar unit.abyte = abyte Unit.abool = = Abool Unit.along = = along Float.floattointbits(unit.afloat) = = Float.floattointbits(afloat) Double.doubletolongbits(unit.adouble) = = Double.doubletolongbits(adouble) unit.aObject.equals (aobject) equalsints (unit.ints) equ Alsunits (unit.

[] args) {CollectionNewHashset(); for(inti = 0; I ) {C.add (NewTeacher (i)); } System.out.println ("Collection" +c); Teacher T1=NewTeacher (1); System.out.println ("Teacher" +t1); System.out.println (C.contains (t1)); }}View CodeAfter execution, you can see:Collection, [Teacher [Id=0], Teacher [id=1], Teacher [id=2], Teacher [id=3], Teacher [id=4Teacher [id=] 1]falseView CodeIt is clear that the collection considers that the object with ID 1 does not exist in the collection.Because, the coll

the enumerated Constant Value) is returned ). If we want to get the expected results, we need to rewrite the tostring method. package mark.demo;public class EnumDemo {public static void main(String[] args) {for (Color color : Color.values()) {System.out.println(color);}}public enum Color {RED("red color", 0), GREEN("green color", 1), BLUE("blue color", 2), YELLOW("yellow color", 3);Color(String name, int id) {_name = name;_id = id;}private String _name;private int _id;public String getName()