使用类方法在ArrayList中查找类似的整数

Question

我需要遍历对象和ArrayList对象并查找具有多个对象相同值的变量。如下面的例子，我正在浏览一个ArrayList，它有一个子类。我想要做的是找出一个房子或公寓共享这个示例代码相同的列表号码。我尝试使用双循环，并使用方法（sameListingNum）进行增强循环，并且无法解决问题。

谢谢

// main client class 
public static void main(String[] args) 
    { 
     ArrayList<House> listings = new ArrayList(); 

     listings.add(new House(0001, 200000.00)); 
     listings.add(new House(0201, 200000.00)); 
     listings.add(new House(0001, 200000.00)); 
     listings.add(new House(0401, 200000.00)); 
     listings.add(new House(0031, 200000.00)); 
     listings.add(new Condo(0401, 200000.00, 4)); 
     listings.add(new Condo(0001, 120000.00, 3)); 
     listings.add(new Condo(0301, 220000.00, 2)); 
     listings.add(new Condo(0001, 130000.00, 3)); 
     listings.add(new Condo(0201, 130000.00, 3)); 

     for(House currentHouse: listings) 
     System.out.println(currentHouse); 
     for(int i=0; i<listings.size()-1; i++) 
     { 
     for(int j=i+1; j<listings.size(); j++) 
     { 

     } 
     } 

// House Class 
public class House 
{ 
    public int listingNum; 
    public double price; 

    public House() 
    { 
    listingNum = 0; 
    price = 0.00; 
    } 
    public House(int newListingNum, double newPrice) 
    { 
    listingNum = newListingNum; 
    price = newPrice; 
    } 
    public int getListingNum() 
    { 
    return listingNum; 
    } 
    public double getPrice() 
    { 
    return listingNum; 
    } 
    public String toString() 
    { 
    return ("Listing number: "+listingNum+", Price: "+price); 
    } 
    public boolean sameListingNum(Object other) 
    { 
    if(!(other instanceof House)) 
     return false; 
    else { 
     House objHouse = (House)other; 
     if(listingNum - objHouse.getListingNum() == 0) 
     { 
     System.out.println("Same listing numbers: " 
     +listingNum+", "+objHouse.getListingNum()); 
     return true; 
     } 
     else 
     return false; 
    } 
    } 
} 

// Condo Class 
public class Condo extends House 
{ 
    public int connectedUnits; 

    public Condo() 
    { 
    super(); 
    connectedUnits = 0; 
    } 
    public Condo(int newListingNum, double newPrice, int newConUnits) 
    { 
    super(newListingNum, newPrice); 
    connectedUnits = newConUnits; 
    } 

    public double getPrice() 
    { 
    return price; 
    } 
    public int getListingNum() 
    { 
    return listingNum; 
    } 
    public int getConnectedUnits() 
    { 
    return connectedUnits; 
    } 
    public String toString() 
    { 
    return super.toString()+", Number of connected unints: "+connectedUnits; 
    } 

public boolean sameListingNum(Object other) 
      { 
      if(!(other instanceof House)) 
       return false; 
      else { 
       House objHouse = (House)other; 
       if(listingNum - objHouse.getListingNum() == 0) 
       { 
       System.out.println("Same listing numbers: " 
       +listingNum+", "+objHouse.getListingNum()); 
       return true; 
       } 
       else 
       return false; 
      } 
     } 

Answer 1

您可以将它用列表的地图，像地图>组。

然后你循环你的名单和每个房子/公寓你把它放在同一个列表编号的组中。最后，你会得到一个地图，每个入口都有相同房产号码的房屋/公寓。

这里的样本：

Map<Integer, List<House>> groups = new HashMap<Integer, List<House>>(); 
for (House house:listings) { 
    List<House> group = groups.get(house.getListingNum()); 
    if (group == null) { 
    group = new ArrayList<House>(); 
    groups.put(house.getListingNum(), group); 
    } 
    group.add(house); 
} 

for (Entry<Integer, List<House>> entry:groups.entrySet()) System.out.println("Listing Number "+entry.getKey()+" Houses/condos: "+entry.getValue()); 

Answer 2

试试这个：

foreach(House h in listings) 
{ 
if(listings.Exists(p => p.sameListingNum(h))) 
{ 
//do something 
} 
} 

Answer 3

其他2个答案都将alternativly工作，你可以实现在众议院可比...如。

public class House implements Comparable<House> 

@Override 
public int compareTo(final House o) { 
    return listingNum - o.listingNum; 
} 

然后在你的主要方法。对收藏集进行排序，并检查前一行是否始终具有相同的ID。

Collections.sort(listings); 

    int previousListing = Integer.MIN_VALUE; 

    for (House currentHouse : listings) { 
     if (currentHouse.getListingNum() == previousListing){ 
      System.out.println("Duplicate for " + currentHouse.getListingNum()); 
     } 
     previousListing = currentHouse.getListingNum(); 
    } 

请选择。