What is comparable and comparator in Java?

What is comparable and Comparator in Java with example?

Comparable is meant for objects with natural ordering which means the object itself must know how it is to be ordered. For example Roll Numbers of students. … Logically, Comparable interface compares “this” reference with the object specified and Comparator in Java compares two different class objects provided.

What is the use of Comparator and comparable in Java?

Comparable v/s Comparator in Java

Comparable interface is used to sort the objects with natural ordering. Comparator in Java is used to sort attributes of different objects. Comparable interface compares “this” reference with the object specified. Comparator in Java compares two different class objects provided.

What is a Comparator in Java?

Java Comparator interface is used to order the objects of a user-defined class. This interface is found in java. util package and contains 2 methods compare(Object obj1,Object obj2) and equals(Object element).

What is Comparator example?

Comparator Interface in Java with Examples. Syntax: public int compare(Object obj1, Object obj2): Suppose we have an Array/ArrayList of our own class type, containing fields like roll no, name, address, DOB, etc, and we need to sort the array based on Roll no or name?

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What is difference between compare and compareTo in Java?

compare() is from the Comparator interface. Both methods do the same thing, but each interface is used in a slightly different context. The Comparable interface is used to impose a natural ordering on the objects of the implementing class. The compareTo() method is called the natural comparison method.

What is writable comparable?

A Writable which is also Comparable . WritableComparable s can be compared to each other, typically via Comparator s. Any type which is to be used as a key in the Hadoop Map-Reduce framework should implement this interface.

What is iterator in Java?

Iterator in Java. In Java, an Iterator is one of the Java cursors. Java Iterator is an interface that is practiced in order to iterate over a collection of Java object components entirety one by one. … The Java Iterator also helps in the operations like READ and REMOVE.

How do you sort an ArrayList?

To sort the ArrayList, you need to simply call the Collections. sort() method passing the ArrayList object populated with country names. This method will sort the elements (country names) of the ArrayList using natural ordering (alphabetically in ascending order).