Java LinkedList类

Java LinkedList类使用双链表来存储元素。它提供了一个链表数据结构。它继承了AbstractList类并实现List和Deque接口。

关于Java LinkedList的要点是：

• Java LinkedList类可以包含重复的元素。
• Java LinkedList类维护插入顺序。
• Java LinkedList类不同步。
• 在Java LinkedList类中, 操作是快速的, 因为不需要进行任何移位。
• Java LinkedList类可以用作列表, 堆栈或队列。

LinkedList类的层次结构

如上图所示, Java LinkedList类扩展了AbstractSequentialList类并实现了List和Deque接口。

双链表

在双向链表的情况下, 我们可以从两侧添加或删除元素。

LinkedList类声明

我们来看一下java.util.LinkedList类的声明。

public class LinkedList<E> extends AbstractSequentialList<E> implements List<E>, Deque<E>, Cloneable, Serializable

Java LinkedList的构造方法

Java LinkedList的方法

Java LinkedList示例

import java.util.*;
public class LinkedList1{
 public static void main(String args[]){

  LinkedList<String> al=new LinkedList<String>();
  al.add("Ravi");
  al.add("Vijay");
  al.add("Ravi");
  al.add("Ajay");

  Iterator<String> itr=al.iterator();
  while(itr.hasNext()){
   System.out.println(itr.next());
  }
 }
}

Output: Ravi
       Vijay
       Ravi
       Ajay

Java LinkedList示例添加元素

在这里, 我们看到了添加元素的不同方法。

import java.util.*;
public class LinkedList2{
 public static void main(String args[]){
 LinkedList<String> ll=new LinkedList<String>();
		   System.out.println("Initial list of elements: "+ll);
		   ll.add("Ravi");
		   ll.add("Vijay");
		   ll.add("Ajay");
		   System.out.println("After invoking add(E e) method: "+ll);
		   //Adding an element at the specific position
		   ll.add(1, "Gaurav");
    	   System.out.println("After invoking add(int index, E element) method: "+ll);
    	   LinkedList<String> ll2=new LinkedList<String>();
    	   ll2.add("Sonoo");
		   ll2.add("Hanumat");
		   //Adding second list elements to the first list
		   ll.addAll(ll2);
		   System.out.println("After invoking addAll(Collection<? extends E> c) method: "+ll);
    	   LinkedList<String> ll3=new LinkedList<String>();
    	   ll3.add("John");
		   ll3.add("Rahul");
		   //Adding second list elements to the first list at specific position
		   ll.addAll(1, ll3);
		   System.out.println("After invoking addAll(int index, Collection<? extends E> c) method: "+ll);
    	   //Adding an element at the first position
		   ll.addFirst("Lokesh");
		   System.out.println("After invoking addFirst(E e) method: "+ll);
		   //Adding an element at the last position
    	   ll.addLast("Harsh");
    	   System.out.println("After invoking addLast(E e) method: "+ll);
		   
 }
}

Initial list of elements: []
After invoking add(E e) method: [Ravi, Vijay, Ajay]
After invoking add(int index, E element) method: [Ravi, Gaurav, Vijay, Ajay]
After invoking addAll(Collection<? extends E> c) method: 
[Ravi, Gaurav, Vijay, Ajay, Sonoo, Hanumat]
After invoking addAll(int index, Collection<? extends E> c) method: 
[Ravi, John, Rahul, Gaurav, Vijay, Ajay, Sonoo, Hanumat]
After invoking addFirst(E e) method: 
[Lokesh, Ravi, John, Rahul, Gaurav, Vijay, Ajay, Sonoo, Hanumat]
After invoking addLast(E e) method: 
[Lokesh, Ravi, John, Rahul, Gaurav, Vijay, Ajay, Sonoo, Hanumat, Harsh]

Java LinkedList示例删除元素

在这里, 我们看到了删除元素的不同方法。

import java.util.*;
public class LinkedList3 {

	    public static void main(String [] args)
	    {
	       LinkedList<String> ll=new LinkedList<String>();
		   ll.add("Ravi");
		   ll.add("Vijay");
		   ll.add("Ajay");
		   ll.add("Anuj");
		   ll.add("Gaurav");
		   ll.add("Harsh");
		   ll.add("Virat");
		   ll.add("Gaurav");
		   ll.add("Harsh");
		   ll.add("Amit");
		   System.out.println("Initial list of elements: "+ll);
		 //Removing specific element from arraylist
		      ll.remove("Vijay");
		      System.out.println("After invoking remove(object) method: "+ll); 
		 //Removing element on the basis of specific position
		      ll.remove(0);
		      System.out.println("After invoking remove(index) method: "+ll); 
		      LinkedList<String> ll2=new LinkedList<String>();
		      ll2.add("Ravi");
		      ll2.add("Hanumat");
		 // Adding new elements to arraylist
		      ll.addAll(ll2);
		      System.out.println("Updated list : "+ll); 
		 //Removing all the new elements from arraylist
		      ll.removeAll(ll2);
		      System.out.println("After invoking removeAll() method: "+ll); 
		 //Removing first element from the list
		      ll.removeFirst();
		      System.out.println("After invoking removeFirst() method: "+ll);
		  //Removing first element from the list
		      ll.removeLast();
		      System.out.println("After invoking removeLast() method: "+ll);
		  //Removing first occurrence of element from the list
		      ll.removeFirstOccurrence("Gaurav");
		      System.out.println("After invoking removeFirstOccurrence() method: "+ll);
		  //Removing last occurrence of element from the list
		      ll.removeLastOccurrence("Harsh");
		      System.out.println("After invoking removeLastOccurrence() method: "+ll);

		      //Removing all the elements available in the list     
		      ll.clear();
		      System.out.println("After invoking clear() method: "+ll); 
	   }
	}

Initial list of elements: [Ravi, Vijay, Ajay, Anuj, Gaurav, Harsh, Virat, Gaurav, Harsh, Amit]
After invoking remove(object) method: [Ravi, Ajay, Anuj, Gaurav, Harsh, Virat, Gaurav, Harsh, Amit]
After invoking remove(index) method: [Ajay, Anuj, Gaurav, Harsh, Virat, Gaurav, Harsh, Amit]
Updated list : [Ajay, Anuj, Gaurav, Harsh, Virat, Gaurav, Harsh, Amit, Ravi, Hanumat]
After invoking removeAll() method: [Ajay, Anuj, Gaurav, Harsh, Virat, Gaurav, Harsh, Amit]
After invoking removeFirst() method: [Gaurav, Harsh, Virat, Gaurav, Harsh, Amit]
After invoking removeLast() method: [Gaurav, Harsh, Virat, Gaurav, Harsh]
After invoking removeFirstOccurrence() method: [Harsh, Virat, Gaurav, Harsh]
After invoking removeLastOccurrence() method: [Harsh, Virat, Gaurav]
After invoking clear() method: []

Java LinkedList示例, 以反转元素列表

import java.util.*;
public class LinkedList4{
 public static void main(String args[]){

  LinkedList<String> ll=new LinkedList<String>();
		   ll.add("Ravi");
		   ll.add("Vijay");
		   ll.add("Ajay");
		   //Traversing the list of elements in reverse order
		   Iterator i=ll.descendingIterator();
		   while(i.hasNext())
		   {
			   System.out.println(i.next());
		   }
		   
 }
}

Output: Ajay
Vijay
Ravi

Java LinkedList示例：书籍

import java.util.*;
class Book {
int id;
String name, author, publisher;
int quantity;
public Book(int id, String name, String author, String publisher, int quantity) {
	this.id = id;
	this.name = name;
	this.author = author;
	this.publisher = publisher;
	this.quantity = quantity;
}
}
public class LinkedListExample {
public static void main(String[] args) {
	//Creating list of Books
	List<Book> list=new LinkedList<Book>();
	//Creating Books
	Book b1=new Book(101, "Let us C", "Yashwant Kanetkar", "BPB", 8);
	Book b2=new Book(102, "Data Communications & Networking", "Forouzan", "Mc Graw Hill", 4);
	Book b3=new Book(103, "Operating System", "Galvin", "Wiley", 6);
	//Adding Books to list
	list.add(b1);
	list.add(b2);
	list.add(b3);
	//Traversing list
	for(Book b:list){
	System.out.println(b.id+" "+b.name+" "+b.author+" "+b.publisher+" "+b.quantity);
	}
}
}

输出：

101 Let us C Yashwant Kanetkar BPB 8
102 Data Communications & Networking Forouzan Mc Graw Hill 4
103 Operating System Galvin Wiley 6