java 将 LinkedHashset 内容复制到新的 ArrayList？
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Copying LinkedHashset content to new ArrayList?
提问by user3289108
I've a listView that has some content initially. If the same content it gets, i removed the duplication through linkedhashset. Now, i want copy the linkedhashsetcontents i.e without duplication contents to new ArrayList.
我有一个 listView 最初有一些内容。如果它获得相同的内容，我通过linkedhashset. 现在，我想将linkedhashset内容复制到 new ，即没有重复的内容ArrayList。
I tried to copy through
我试图复制
p.addAll(0,lhm); // P is the instance of ArrayList and lhm is linkedHashset instance
But, the ArrayListincludes the duplication content too.
但是，也ArrayList包括重复的内容。
Example :
例子 ：
ArrayList<Price> p = new ArrayList<Price>();
p.add(new Price("Banana", 60));
p.add(new Price("Apple", 80));
LinkedHashSet<Price> lhm = new LinkedHashSet<Price>(p);
lhm.add(new Price("Banana", 20));
lhm.add(new Price("Apple", 40));
lhm.add(new Price("Orange", 30));
for(Price pr:lhm)
{
System.out.println(pr);
}
Price duplicate = new Price("Banana", 20);
System.out.println("inserting duplicate object...");
lhm.add(duplicate);
lhm.add(new Price("Apple", 40));
p.addAll(0,lhm);
System.out.println("After insertion:");
for(Price pr:lhm)
{
System.out.println(pr);
}
for (int i = 0; i < p.size(); i++) {
System.out.println(p.get(i).getItem() +"-" +p.get(i).getPrice());
}
Price.class
价格等级
class Price
{
private String item;
private int price;
public Price(String itm, int pr)
{
this.item = itm;
this.price = pr;
}
public int hashCode()
{
System.out.println("In hashcode");
int hashcode = 0;
hashcode = price;
//System.out.println(hashcode);
hashcode+= item.hashCode();
// System.out.println(hashcode);
return hashcode;
}
public boolean equals(Object obj)
{
System.out.println("In equals");
if (obj instanceof Price)
{
Price pp = (Price) obj;
return (pp.item.equals(this.item) && pp.price == this.price);
}
else
{
return false;
}
}
public String getItem()
{
return item;
}
public void setItem(String item)
{
this.item = item;
}
public int getPrice()
{
return price;
}
public void setPrice(int price)
{
this.price = price;
}
public String toString()
{
return "item: "+item+" price: "+price;
}
}
Output :
输出 ：
In hashcode
In hashcode
In hashcode
In hashcode
In hashcode
item: Banana price: 60
item: Apple price: 80
item: Banana price: 20
item: Apple price: 40
item: Orange price: 30
inserting duplicate object...
In hashcode
In equals
In hashcode
In equals
//iterating linkedhasset content
After insertion:
item: Banana price: 60
item: Apple price: 80
item: Banana price: 20
item: Apple price: 40
item: Orange price: 30
// iterating ArrayList p content
Banana-60
Apple-80
Banana-20
Apple-40
Orange-30
Banana-60
Apple-80 <-- duplicate
回答by AKS
The following line just inserts all the elements into the arraylist starting from the 0th index
以下行只是从第 0 个索引开始将所有元素插入到 arraylist 中
p.addAll(0,lhm);
And, the elements which were added using these lines were still present in the arraylist:
而且，使用这些行添加的元素仍然存在于数组列表中：
p.add(new Price("Banana", 60));
p.add(new Price("Apple", 80));
So, you should clear the array list before adding the items from the linkedhashset, in case you don't want the duplicates. i.e.
因此，您应该在从linkedhashset 添加项目之前清除数组列表，以防您不想要重复项。IE
p.clear();
p.addAll(lhm); // and, at this point you don't need the index.
回答by Anuj Dhiman
See this full solution may be help you
看到这个完整的解决方案可能对你有帮助
import java.util.ArrayList;
import java.util.LinkedHashSet;
import java.util.List;
import java.util.Set;
public class LinkedHashSetToList {
public static void main(String[] args) {
Set<String> lhs = new LinkedHashSet<String>();
lhs.add("mumbai");
lhs.add("delhi");
lhs.add("kolkata");
lhs.add("chandigarh");
lhs.add("dehradun");
//print linkedhashset
System.out.println("lhs is = "+lhs);
List<String> list = new ArrayList<String>(lhs);
// print arraylist
System.out.println("ArrayList Is = "+list);
}
}
Output:
输出：
lhs is = [mumbai, delhi, kolkata, chandigarh, dehradun]
ArrayList Is = [mumbai, delhi, kolkata, chandigarh, dehradun]
Reference : How to Convert a LinkedHashSet to ArrayList
回答by shmosel
A Setwill only ensure that its ownelements are unique. You can't expect ArrayListto exclude duplicates unless the entirecollection is filtered through a set. For example:
ASet只会确保它自己的元素是唯一的。ArrayList除非整个集合都通过一个集合过滤，否则您不能期望排除重复项。例如：
...
p.addAll(0,lhm);
p = new ArrayList<String>(new HashSet<String>(p));
