LinkedHashSet是Java Collection Framework的一個類，它實作了Set介面並擴充了HashSet類別。它是一種鍊錶類型的集合類別。它按照插入的順序儲存和返回對象，因此不允許重複的對象。在本文中，我們將使用內建方法'contains()'從LinkedHashSet中尋找使用者定義的物件。使用者定義的物件是透過建構函數來建立的。
讓我們簡要介紹一下我們在範例程式中將使用的兩個重要的內建方法。
它接受一個參數並將其添加到集合的末尾。它與LinkedHashSet類別的實例一起使用。
nameOfobject.add(argument)
Here, argument signifies the value that we are going to store in the set.
It accepts an instance of LinkedHashSet class and checks whether the passed instance is available in the set or not. If the set contains that instance then it returns true otherwise false. Its return type instance then it returns true otherwise false. Its return type islean .
nameOfobject.contains(Object)
Here,
Object 表示我們需要驗證的物件的名稱
nameOfobject signifies the object of that class which conatins all the collections.
The following example illustrates how we can use contains() method to find the user-defined objects from a LinkedHashSet collection.
首先，定義一個名為'LinkHset' 的類，在類別內部宣告兩個變量，並定義一個建構函數，該構造函數帶有兩個參數'item' 和'price'，分別為字串和整數類型。
Now, use the 'contains()' method to check whether the specified object is available or not.
import java.util.*;
public class LinkHset {
String item;
int price;
LinkHset(String item, int price) { // constructor
// this keyword shows these variables belong to constructor
this.item = item;
this.price = price;
}
public static void main(String[] args) {
// defining the objects
LinkHset col1 = new LinkHset("TShirt", 59);
LinkHset col2 = new LinkHset("Trouser", 60);
LinkHset col3 = new LinkHset("Shirt", 45);
LinkHset col4 = new LinkHset("Watch", 230);
LinkHset col5 = new LinkHset("Shoes", 55);
// Declaring collection of LinkedHashSet
LinkedHashSet<LinkHset> linkHcollection = new
LinkedHashSet<LinkHset>();
// Adding the user-defined objects to the collection
linkHcollection.add(col1);
linkHcollection.add(col2);
linkHcollection.add(col3);
linkHcollection.add(col4);
linkHcollection.add(col5);
// to print the all objects
for (LinkHset print : linkHcollection) {
System.out.println("Item: " + print.item + ", " + "Price: "
+ print.price);
}
// to find a specified objects
if(linkHcollection.contains(col5)) {
System.out.println("Set contains the specified collection: "
+ col5.item);
} else {
System.out.println("Sorry! couldn't find the object");
}
}
}
Item: TShirt, Price: 59 Item: Trouser, Price: 60 Item: Shirt, Price: 45 Item: Watch, Price: 230 Item: Shoes, Price: 55 Set contains the specified collection: Shoes
在下面的範例中，我們將使用contains()方法和迭代器來從LinkedHashSet集合中尋找使用者定義的方法。
import java.util.*;
public class LinkHset {
String item;
int price;
LinkHset(String item, int price) { // constructor
// this keyword shows these variables belong to constructor
this.item = item;
this.price = price;
}
public static void main(String[] args) {
// defining the objects
LinkHset col1 = new LinkHset("TShirt", 59);
LinkHset col2 = new LinkHset("Trouser", 60);
LinkHset col3 = new LinkHset("Shirt", 45);
LinkHset col4 = new LinkHset("Watch", 230);
LinkHset col5 = new LinkHset("Shoes", 55);
// Declaring collection of LinkedHashSet
LinkedHashSet<LinkHset> linkHcollection = new LinkedHashSet<
LinkHset>();
// Adding the user-defined objects to the collection
linkHcollection.add(col1);
linkHcollection.add(col2);
linkHcollection.add(col3);
linkHcollection.add(col4);
linkHcollection.add(col5);
// creating iterator interface to iterate through objects
Iterator<LinkHset> itr = linkHcollection.iterator();
while (itr.hasNext()) {
// to print the specified object only
if(linkHcollection.contains(col5)) {
System.out.println("Item: " + col5.item + ", " +
"Price: " + col5.price);
break;
} else {
System.out.println("Sorry! couldn't find the object");
break;
}
}
}
}
Item: Shoes, Price: 55
我們透過介紹實作Set介面並擴充HashSet類別的LinkedHashSet類別來開始這篇文章。在下一節中，我們討論了它的內建方法'add()'和'contains()'，這些方法幫助我們從LinkedHashSet中取得使用者定義的對象
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