[Java] HashCode and equals overrides
- Object HashCode () and equals ()
as mentioned above,
equals () is comparing the addresses of obj.
hashCode () is calculated on the native side. In other words, it is calculated on the C / C ++ side.
Then, when comparing ==, it becomes false.
- String HashCode () and equals ()
String inherits object.
String overrides HashCode () and equals ().
The above equals
-
True if the object has the same address
-
False if the comparison string class is not String
-
False if the comparison string class lengths are not the same 4, compare in loop, false if wrong
-
True when the loop is completed
-
HashCode () and equals () on your own
private static class Person { int age; String name;
public Person(String name, int age) { this.name = name; this.age = age; } public String toString() { return name + " - " +age; } /** * @desc */ @Override public boolean equals(Object obj){ if(obj == null){ return false; } if(this == obj){ return true; } if(this.getClass() != obj.getClass()){ return false; } Person person = (Person)obj; return name.equals(person.name) && age==person.age; } @Override public int hashCode() { return this.name.hashCode(); }}
Sample code https://github.com/YanHengGo/java/tree/master/04_hashcode
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