comparable

问题 This question already has an answer here : Java generics issue: Class “not within bounds of type-variable” error. (1 answer) Closed 4 years ago . I'm implementing a generic AVL tree but I'm having some compilation error. My AVL Tee has to deal with Node<T> of type T. In the example, the type is Event class.I want to compare the node. But each type of data has to be compared differently, for that, i'm passing the comparison to the data itself to do the comparison. I tried to make the Node

问题 So I've been given the following problem: Write a program that creates a List of Rationals and sorts them into increasing order. Use appropriate methods from the Collections Framework classes to sort the elements into increasing order. I've created a 'Rational' class to represent rational numbers and I've also made the list of random Rational numbers. But I'm having trouble figuring out a way to implement a method of sorting the list. Here's samples of the code before I go on further: public

问题 What I want to do is use the compareTo() method to compare removedItemFromList1 and removedItemFromList2, then insert whichever value is smaller into the modifiedList3 and put the larger of the two removedFromList 1 or 2 back into its original list. If I had hair long enough to pull, it would have been pulled out by now...Am I not casting correctly? How do I correctly go about using the compareTo() method to accomplish this? public class List<Integer> implements Comparable { private ListNode

问题 Anybody knows how to write the piece of code below using generics AND avoiding compiler warnings ? (@SuppressWarnings("unchecked") is considered cheating). And, maybe, checking via generics that the type of "left" is the same as the type of "right" ? public void assertLessOrEqual(Comparable left, Comparable right) { if (left == null || right == null || (left.compareTo(right) > 0)) { String msg = "["+left+"] is not less than ["+right+"]"; throw new RuntimeException("assertLessOrEqual: " + msg)

问题 I am somewhat familiar with sorting in Scala using Ordering 's, however I would like to sort some objects which are defined in Java. They are Comparable (not Comparable[T] ) and final : final class Term implements Comparable { ... } (this is actually Lucene's Term class, and no I can't change the version of Lucene). I first hoped there was an implicit somewhere: terms.sorted //fail - no implicit ordering So maybe I could make it ordered? class OrderedTerm extends Term with Ordering[Term] /

问题 I've got a class, "Accumulator", that implements the Comparable compareTo method, and I'm trying to put these objects into a HashSet. When I add() to the HashSet, I don't see any activity in my compareTo method in the debugger, regardless of where I set my breakpoints. Additionally, when I'm done with the add()s, I see several duplicates within the Set. What am I screwing up, here; why is it not Comparing, and therefore, allowing the dupes? Thanks, IVR Avenger 回答1: What am I screwing up, here

问题 I know that compareTo returns a negative or positive result on how well one string correlates to the other, but then why: public class Test { public static void main(String[] args) { String y = "ab2"; if(y.compareTo("ac3") == -1) { System.out.println("Test"); } } } is true and public class Test { public static void main(String[] args) { String y = "ab2"; if(y.compareTo("ab3") == -1) { System.out.println("Test"); } } } is also true? 回答1: The general contract of Comparable.compareTo(o) is to

问题 I am creating a simple program to learn about the Java Comparator class. I have sorted an Arraylist into order but now I want to sort the list in descending order but am having problems in where to call the .reverseOrder() method as I have used an inner class that implements Comparator<Song> (song being a song class which houses getters and setter methods). Here is my SongSort class which houses the sorting process etc.; import java.util.*; import java.io.*; public class SongSort { ArrayList

问题 Today I was asked this interview question: If I have a Person class with name , age and salary fields, and I put 100 new instances of this Person in an ArrayList , and then do Collections.sort(list) , then on what parameter will the list be sorted? I understand that I need to have the Person class implement Comparable and then override compareTo , but if I don't do that, what will happen? 回答1: It wouldn't compile: the 1-argument version of Collections.sort expects a list of Comparable s.

问题 If I have a class Person that implements Comparable (compares personA.height to personB.height , for example), is it possible to use personA < personB as a substitute for personA.compareTo(personB) == -1? Are there any issues in doing this or do I need to overload operators? 回答1: There is no operator overloading in Java. You probably come from a C++ background. You have to use the compareTo method. 回答2: No, it isn't possible to use personA < personB as a substitute. And you can't overload