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How to use List interface |
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List interface is an extension of Collection interface. List interface indicates the behavior of the collection of objects. It allows duplicate objects and one or more elements to be null.
Useful methods of the List Interface:
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Method
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Usage
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add()
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Adds an
objects to the collection
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clear()
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Removes all objects from the
collection.
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contains()
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Returns true if a special object
is an element with in the collection.
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get()
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Returns the element at the
specified index position in this collection.
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isEmpty()
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Returns true if the collection
has no elements.
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listIterator()
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Returns a ListItertor object for
the collection which may then be used to retrieve an object.
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Remove()
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Removes the element at the
specified index position in this collection.
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size()
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Returns the number of elements
in the collection.
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In this code ListIterator is used for reading the objects of the list. It allows reading objects from the collection in both the forward and backward directions.
import java.util.*;
public class DemoList {
public static void main(String[] args) {
List ls = new LinkedList();
for(int i=1; i<=5; i++){
ls.add(new StringBuffer("Object " + i));
}
//display how many objects are in the collection
System.out.println("The collection has " + ls.size() + "objects");
//Instantiate a ListIterator
ListIterator li = ls.listIterator();
System.out.println("Forward Reading");
//Forward direction
while(li.hasNext()){
System.out.println(" " + li.next());
}
System.out.println("Backward Reading");
//backword direction
while(li.hasPrevious()){
System.out.println(" " + li.previous());
}
}
}
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Output Screen:
The collection has 5objects
Forward Reading
Object 1
Object 2
Object 3
Object 4
Object 5
Backward Reading
Object 5
Object 4
Object 3
Object 2
Object 1
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