equals

问题 This is the most crazy thing I have seen in java (1.6): Set<ActionPlan> actionPlans = assessment.getActionPlans(); //getActionPlans() returns a java.util.HashSet<ActionPlan> ActionPlan actionPlan = actionPlans.iterator().next(); assertTrue(actionPlan1.equals(actionPlan)); assertEquals(actionPlan1.hashCode(), actionPlan.hashCode()); assertTrue(actionPlans.contains(actionPlan1)); The first two asserts pass but the last one fails. I'm not giving you details on the ActionPlan and Assessment

问题 This is the most crazy thing I have seen in java (1.6): Set<ActionPlan> actionPlans = assessment.getActionPlans(); //getActionPlans() returns a java.util.HashSet<ActionPlan> ActionPlan actionPlan = actionPlans.iterator().next(); assertTrue(actionPlan1.equals(actionPlan)); assertEquals(actionPlan1.hashCode(), actionPlan.hashCode()); assertTrue(actionPlans.contains(actionPlan1)); The first two asserts pass but the last one fails. I'm not giving you details on the ActionPlan and Assessment

问题 var a = new double[] {1, 2, 3}; var b = new double[] {1, 2, 3}; System.Console.WriteLine(Equals(a, b)); // Returns false However, I'm looking for a way to compare arrays which would compare the internal values instead of refernces. Is there a built in way to do this in .NET? Also, while I understand Equals comparing references, GetHashCode returns different values for these two arrays also, which I feel shouldn't happen, since they have the same internal values. 回答1: I believe you are looking

问题 Is there ever a situation where using equals(Boolean) and == would return different results when dealing with Boolean objects? Boolean.TRUE == myBoolean; Boolean.TRUE.equals(myBoolean); I'm not thinking about primitive types here, just Boolean objects. 回答1: How about: System.out.println(new Boolean(true) == new Boolean(true)); System.out.println(new Boolean(true) == Boolean.TRUE); (both print false, for the same reason as any other type of objects). 回答2: It would be dangerous to use ==

问题 I have a class with a float field. For example: public class MultipleFields { final int count; final float floatValue; public MultipleFields(int count, float floatValue) { this.count = count; this.floatValue = floatValue; } } I need to be able to compare instances by value. Now how do I properly implement equals & hashCode ? The usual way to implement equals and hashCode is to just consider all fields. E.g. Eclipse will generate the following equals : public boolean equals(Object obj) { //

问题 I have a class that accepts a generic type , and I want to override the equals method in a non-awkward way (i.e. something that looks clean and has minimal amount of code, but for a very general use case). Right now I have something like this: public class SingularNode<T> { private T value; @SuppressWarnings("unchecked") @Override public boolean equals(Object other){ if(other instanceof SingularNode<?>){ if(((SingularNode<T>)other).value.equals(value)){ return true; } } return false; } }

问题 I am writing a class Vec2D , representing a 2 dimensional vector. I store x and y in double s. When asked to generate equals(Object obj and hashCode() , eclipse generated this: @Override public int hashCode() { final int prime = 31; int result = 1; long temp; temp = Double.doubleToLongBits(x); result = prime * result + (int) (temp ^ (temp >>> 32)); temp = Double.doubleToLongBits(y); result = prime * result + (int) (temp ^ (temp >>> 32)); return result; } @Override public boolean equals(Object

问题 By default hashCode and equals works fine. I have used objects with hash tables like HashMap, without overriding this methods, and it was fine. For example: public class Main{ public static void main(String[] args) throws Exception{ Map map = new HashMap<>(); Object key = new Main(); map.put(key, "2"); Object key2 = new Main(); map.put(key2, "3"); System.out.println(map.get(key)); System.out.println(map.get(key2)); } } This code works fine. By default hashCode returning memory address of

问题 I'm making a JOptionpane where the user can has to enter hes name. So it can't be empty and it can't be a number The empty part is working but now I have to find a solution for the number part As you can see in my code I made a while loop to check if "naam" isn't empty. Now I need to find a way to check if "naam" isn't a number. String naam = JOptionPane.showInputDialog("Geef uw naam in: "); while (naam.equals("")) { JOptionPane.showMessageDialog(null, "Geef een naam in", "Geef naam",

问题 I have some code where I try to use the HashSet.retainAll() function. In the example code below, the HashSet contains the interface IPerson , but the equals functions in object Person is never reached. I have even tried to expose the equals function in the interface and several other things. I feel I have tried everything. How can I make retainAll() use my implemented equal function? class Person implements IPerson { private String name; public Person(String name){ this.name = name; }