So this compareTo method compares CarOwner objects and if the calling object is earlier in chronological time in comparison to the argument returns -1, if the calling object is later in chronological time in comparison to the argument returns 1, if the calling object and argument are the same in.
For example, Map. This means it only works when both key and value objects implement equals () properly. This is generally not a very useful order. The way that Map.equals () works is by comparing keys and values using the Object.equals () method. They're naturally sorted in an order that's implied by the hashCode function of the key class, and by the current size of the map. Of course, if you really intend to return some kind of sorted map, then it might be more like private static > Map sortByValues(Map map)īut you need to remember that it's not possible to sort HashMap objects. private static > List sortAndListValues(Map map) In your case, you'd give your method a signature like this, assuming it's going to return a List. Therefore, you could write your method as generic, which means that its signature will list some type parameters, inside characters, possibly with some conditions on those type parameters. Table 11.2 summarizes the methods that objects. You don't need any such condition on the type of the keys in your map. Implementing the Comparable interface allows them to be used as elements in sorted collections and sorted maps. This is the condition that you want the type of the values in your map to obey.
So if you have a type V, then writing V extends Comparable means that one object of type V can be compared to other objects of type V, using the compareTo method. The generic interface that tells you that one object can be compared to another is Comparable. There's no general way of sorting Object, so for this to make sense, you want to restrict your parameter to be a map whose values can be sorted, or to put it another way, can be compared to other objects of the same type. But it only makes sense to do this if the values in your map belong to some type that can be sorted. A Map is a data structure consisting of a set of keys and values in which each key is mapped to a si.
#COMPARETO METHOD MAP JAVA CODE#
Now in this particular case, you seem to be building a sorted list of values from your map. Best Java code snippets using (Showing top 3 results out of 315).
The compiler is your friend - it gives you messages to help you find your errors. Therefore, the compare method is implemented. you end up casting objects to whatever type you need them to be, which is prone to error, and such errors usually only reveal themselves at run time.įinding errors at compile time is better than finding them at run time. The Comparator interface is a functional interface in Java 8, and the method implemented is the compare method.you sacrifice a lot of the type safety that the compiler gives you,.However, it's a bad idea to do that, because For historical reasons it's possible to use them without type parameters, which is what you've done here. I was wondering if this is an efficient way of implementing the compareTo.All of Java's collection classes and interfaces are generics, which means they are intended to be used with type parameters. The natural ordering should be by lName, fName, middleInitial. My object has three fields that make up a name. I'm implementing the compareTo method to set the natural order of an object.
0 kommentar(er)
