java hashcode and equals contract

and equals is the difference is that he returned to the int type, compared to not intuitive. We generally overwrite equals while covering the hashcode to make their logic consistent. For example, if the name and gender are equal even if 2 objects are equal, then the Hashcode method also returns the

effective Java by Joshua Bloch. Writing a good hashCode method is actually quite difficult. This class aims to simplify the process.The following is the approach taken. When appending a data field, the current total was multiplied by the multiplier and then a relevant value for this data type is Added. For example, if the current hashcode are, and the multiplier

Hashcode is a method that has been defined in object, called a hash code, to see how object describes it. /*** Returns A hash code value for the object. This method was * supported for the benefit of hash tables such as those provided by * {@linkJava.util.HashMap}. * The general contract of {@codeHashcode} is: * @codeHashcode} method * must consistently return the same integer, provided no information *

must create a matching hashcode implementation! In addition, implementation of equal should be implemented according to our implementation, which may result in the absence of the same hash code, because they are using an Object implementation.Hashcode conventionsReferences from the original document:General conventions for Hashcode: In a Java applicatio

() method returns false, otherwise it is compared.The JVM default hashcode are not equal, and the object values are not equal. Its inverse proposition is: if the object value is equal, then its hashcode is equal.When overriding Equals (), you must also override Hashcode (). And you need to ensure that objects of equal

from the beginning of learning Java, Hashcode () method is the object class itself has the method, all classes inherit the object, also Hashcode () this method. When you are learning Java, you are told to override the Hashcode method when overriding the

The Hashcode method returns the hash code value of the object.The Hashcode () method can be used to improve the efficiency of the search in the map, map will be based on different hashcode () in different locations, map in the search for an object by Hashcode () to find the corresponding position, and then according to

In Java, there is a rule that two identical objects (that is, the equals operation is true) and their hash code must be the same. There is a Hashcode method in the object class that you can call to view the object's hash code. The following examples illustrate. Copy Code code as follows: Package test; public class Test { public static void

discards the element without saving, and hashes to other addresses. 2.HOW use Hashcode ()? The Java language equal () has five requirements that must be followed for ape design. of symmetry. If a.equal (b) returns "true", b.equal (a) must also return "true".of the reflex. A.equal (a) must return "true".Transitivity. If a.equal (b) returns "true" and B.equal (c) returns "true", C.equal (a) will return "t

One: HashMap---> The underlying storage is entryThe structure of the--->EntryStatic Class EntryFinal K Key;V value;Entryint hash;/*** Creates new entry.*/Entry (int h, K K, v V, entryValue = V;Next = n;key = k;hash = h;}}---> Save or remove the location.(1) When the key is stored, take the key Hascode, then hascode a series of bitwise AND, bitwise XOR and finally get a number, and then take this number and entry[] array length minus one to bitwise AND operation, to find out the array subscript t

.equals (I4) = true I2 = I4 = falseI2.equals (I4) = true I = I2 = trueI1.equals (I) = true I = I4 = trueI4.equals (I) = true Iii. How to Use equals and = for other classesMost of the classes in the API are overwritten by the equa