How to use comparable interface in java

What is comparable in Java with example?

Comparable interface is mainly used to sort the arrays (or lists) of custom objects. Lists (and arrays) of objects that implement Comparable interface can be sorted automatically by Collections. sort (and Arrays.

How do you make a comparable in Java?

To make an object comparable, the class must implement the Comparable interface. negative , if this object is less than the supplied object. zero , if this object is equal to the supplied object. positive , if this object is greater than the supplied object.

How do you implement comparable?

Java provides Comparable interface which should be implemented by any custom class if we want to use Arrays or Collections sorting methods. The Comparable interface has compareTo(T obj) method which is used by sorting methods, you can check any Wrapper, String or Date class to confirm this.

Is comparable a functional interface?

Literally Comparable is a functional interface as it declares one and only one abstract method. But annotating it with @FunctionalInterface would mean that it is documented to be used as a functional interface while that is not the case at all.

What is comparable interface in Java?

Java Comparable interface is used to order the objects of the user-defined class. This interface is found in java. lang package and contains only one method named compareTo(Object). It provides a single sorting sequence only, i.e., you can sort the elements on the basis of single data member only.

What is a TreeSet?

Java TreeSet class implements the Set interface that uses a tree for storage. It inherits AbstractSet class and implements the NavigableSet interface. The objects of the TreeSet class are stored in ascending order. … Java TreeSet class contains unique elements only like HashSet.

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What does the hashCode () method?

Java Object hashCode() is a native method and returns the integer hash code value of the object. … If two objects are equal according to equals() method, then their hash code must be same. If two objects are unequal according to equals() method, their hash code are not required to be different.

How do you sort an ArrayList?

sort() method is used to sort an ArrayList in ascending order, and the Collections. reverse() method is used to reverse the order of items in an ArrayList. When used together, sort() and reverse() can sort the items in an ArrayList in descending order.

What is serialization in Java?

Object Serialization is a process used to convert the state of an object into a byte stream, which can be persisted into disk/file or sent over the network to any other running Java virtual machine. The reverse process of creating an object from the byte stream is called deserialization.

Why would we make a class implement the comparable interface?

The Java Comparable interface is mainly used to sort the arrays or lists of custom objects. … Since all wrapper classes already implement the Java Comparable Interface and provided a default implementation of compareTo() the method, that is why we can use Collections. sort() and Arrays. sort() on these objects.

Can an interface be instantiated?

An interface can’t be instantiated directly. Its members are implemented by any class or struct that implements the interface. A class or struct can implement multiple interfaces. A class can inherit a base class and also implement one or more interfaces.

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What are the benefits of implementing the Comparable interface?

The benefit of implementing the interface is that some methods specifically require object that implements the Comparable interface. It gives them a guarantee that the object you’re passing has a compareTo method with the correct signature.

Can functional interface have more than one method?

A functional interface has only one abstract method but it can have multiple default methods. @FunctionalInterface annotation is used to ensure an interface can’t have more than one abstract method.

When would you use a functional interface?

An interface with only one abstract method is called Functional Interface. It is not mandatory to use @FunctionalInterface, but it’s best practice to use it with functional interfaces to avoid addition of extra methods accidentally. … Interface that contains a “single abstract” method.

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