Java LinkedHashSet类

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📜 Java LinkedHashSet类

📅 最后修改于: 2020-10-12 09:42:11 🧑 作者: Mango

Java LinkedHashSet类是set接口的Hashtable和Linked list实现。它继承了HashSet类并实现Set接口。

关于Java LinkedHashSet类的要点是：

Java LinkedHashSet类仅包含唯一元素，例如HashSet。
Java LinkedHashSet类提供所有可选的set操作，并允许空元素。
Java LinkedHashSet类未同步。
Java LinkedHashSet类维护插入顺序。

LinkedHashSet类的层次结构

LinkedHashSet类扩展了实现Set接口的HashSet类。 Set接口按层次结构顺序继承Collection和Iterable接口。

LinkedHashSet类声明

我们来看一下java.util.LinkedHashSet类的声明。

public class LinkedHashSet extends HashSet implements Set, Cloneable, Serializable

Java LinkedHashSet类的构造方法

Constructor	Description
HashSet()	It is used to construct a default HashSet.
HashSet(Collection c)	It is used to initialize the hash set by using the elements of the collection c.
LinkedHashSet(int capacity)	It is used initialize the capacity of the linked hash set to the given integer value capacity.
LinkedHashSet(int capacity, float fillRatio)	It is used to initialize both the capacity and the fill ratio (also called load capacity) of the hash set from its argument.

Java LinkedHashSet示例

让我们看一下Java LinkedHashSet类的简单示例。在这里，您会注意到元素按插入顺序进行迭代。

import java.util.*;
class LinkedHashSet1{
 public static void main(String args[]){
 //Creating HashSet and adding elements
    LinkedHashSet set=new LinkedHashSet();
   set.add("One");  
   set.add("Two");  
   set.add("Three"); 
   set.add("Four");
   set.add("Five");
   Iterator i=set.iterator();
   while(i.hasNext())
   {
   System.out.println(i.next());
   }
 }
}

One
Two
Three
Four
Five

Java LinkedHashSet示例忽略重复的元素

import java.util.*;
class LinkedHashSet2{
 public static void main(String args[]){
  LinkedHashSet al=new LinkedHashSet();
  al.add("Ravi");
  al.add("Vijay");
  al.add("Ravi");
  al.add("Ajay");
  Iterator itr=al.iterator();
  while(itr.hasNext()){
   System.out.println(itr.next());
  }
 }
}

       Ravi
       Vijay
       Ajay

Java LinkedHashSet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 LinkedHashSetExample {
public static void main(String[] args) {
LinkedHashSet hs=new LinkedHashSet();
//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 hash table
hs.add(b1);
hs.add(b2);
hs.add(b3);
//Traversing hash table
for(Book b:hs){
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