HashMap問題，打印鄰居

我正在使用HashMap。我的代碼會編譯，但是當我運行它時，我沒有得到我應該期待的。我的代碼爲printAllNeighbors和getNeighbor不起作用。誰能幫我。我想我明白我在做什麼，這就是爲什麼我很困惑。HashMap問題，打印鄰居

import java.util.HashMap; 
public class House 
{ 
    private int streetNumber; 
    private String streetName; 
    private String owners; 
    HashMap <String, House> myNeighbors; 

    public House (int streetNumber, String streetName, String lastName) 
    { 
     streetNumber = streetNumber; 
     streetName = streetName; 
     lastName = owners; 
     myNeighbors = new HashMap <String, House>(); 
    } 
    public int getStreetNumber() 
    { 
     return streetNumber; 
    } 
    public String getStreetName() 
    { 
     return streetName; 
    } 
    public String getLastName() 
    { 
     return owners; 
    } 
    public void setStreetNumber(int streetNumber) 
    { 
     streetNumber =this.streetNumber; 
    } 
    public void setStreetName(String streetName) 
    { 
     streetName = this.streetName; 
    } 
    public void setLastName(String lastName) 
    { 
     owners = lastName; 
    } 
    public void addNeighbor (String direction, House h) 
    { 
     myNeighbors = new HashMap <String, House>(); 
    } 
    public House getNeighbor (String direction) 
    { 
     if(direction.equals(direction)){ 
      return getNeighbor(direction); 
     } 
     else{    
      return null; 
     } 
    } 
    public void printAllNeighbors() 
    { 
     for (String key : myNeighbors.keySet()) 
     { 
      System.out.println("\nkey: " + key + " value: " + myNeighbors.get(key)); 
     } 
    } 
    public String toString() 
    { 
     return "Address: " + streetNumber + " " + streetName + "\nOwner: " + owners; 
    } 
    public static void main (String [] args) 
    { 
     House whiteHouse = new House (1600, "Pennsylvania Ave", "Obama"); 
     House jerrysHouse = new House (1602, "Pennsylvania Ave", "Mabrito"); 
     House guentersHouse = new House (1604, "Pennsylvania Ave", "Tusch"); 
     House anasHouse = new House (1609, "Pennsylvania Ave", "Posada"); 

     whiteHouse.addNeighbor("east", jerrysHouse); 
     whiteHouse.addNeighbor("south", guentersHouse); 
     whiteHouse.addNeighbor("north west", anasHouse); 

     System.out.println(whiteHouse);  
     whiteHouse.printAllNeighbors(); 

     System.out.println("****************************** \n" + jerrysHouse); 
     jerrysHouse.printAllNeighbors(); 

     System.out.println("****************************** \n" + guentersHouse); 
     guentersHouse.printAllNeighbors(); 

     System.out.println("****************************** \n" + anasHouse); 
     anasHouse.printAllNeighbors(); 
    } 
}

來源

2015-07-10 Deborah_Watson

我想你需要告訴我們你得到了什麼，以及你的期望。 – ThisClark

我得到空0，業主0，我期待得到白宮，jerrysHouse，guentersHouse等的鄰居。 –

嗨@Deborah_Watson如果任何答案已解決您的問題，請點擊複選標記考慮[接受它]（http://meta.stackexchange.com/q/5234/179419）。這向更廣泛的社區表明，您已經找到了解決方案，併爲答覆者和您自己提供了一些聲譽。沒有義務這樣做。 – gastonmancini

問題是與你的addNeighbor方法，您要創建一個新的HashMap對象每次調用它，而不是將元素添加到地圖的時間。

嘗試使用HashMap put方法。例如：

myNeighbors.put(direction,h);

來源

2015-07-10 03:49:13 gastonmancini

你想做什麼？

public void addNeighbor (String direction, House h) 
    { 
     //myNeighbors = new HashMap <String, House>(); This is not correct 
     myNeighbors.put(direction,h); // use this 
    }

並初始化你映射在像下面開始時，

Map <String, House> myNeighbors= new HashMap<String, House>();

來源

2015-07-10 03:50:08 Ravi

，我發現你的代碼存在以下問題。首先在構造函數中如果你想引用對象字段，你應該使用這個引用，否則它只會更新局部變量。

public House (int streetNumber, String streetName, String lastName) 
{ 
this.streetNumber = streetNumber; 
this.streetName = streetName; 
this.owners = lastName // Note this you were previously assigning value of owner to lastName 
myNeighbors = new HashMap <String, House>(); 
}

，並使用

myNeighbors.put(direction,h);

代替

myNeighbors = new HashMap <String, House>();

來源

2015-07-10 03:59:36

問題是與你的構造和setter方法。你正在做沒有任何作用的作業。例如，

public House (int streetNumber, String streetName, String lastName) 
{ 
    streetNumber = streetNumber; 
    streetName = streetName; 
    lastName = owners; 
    myNeighbors = new HashMap <String, House>(); 
}

從上面的構造函數，你還沒有正確地初始化字段。 'streetNumber'和'streetNames'是你的構造函數中的參數，所以在影子上隱藏（隱藏）私有數據字段'streetNumber'和'streetName'，要訪問這個私有數據字段，你應該使用'this'關鍵字。而不是 lastName =擁有者; 在你的構造函數中，它應該是 owners = lastName; 因此，這是修改後的構造

public House (int streetNumber, String streetName, String lastName) 
{ 
    this.streetNumber = streetNumber; 
    this.streetName = streetName; 
    owners = lastName; 
    myNeighbors = new HashMap <String, House>(); 
}

你的setter方法有同樣的問題，所以對於setStreetNumber（）方法，變化

streetNumber = streetNumber; to 
this.streetNumber = streetNumber;

和setStreetName做同樣的（）方法

來源

2015-07-10 04:08:05 ivange

我已經對你的代碼做了一些修改，以使它在運行時回覆，如果有些東西不符合你的期望

import java.util.HashMap; 
public class House 
{ 
    private int streetNumber; 
    private String streetName; 
    private String owners; 
    HashMap <String, House> myNeighbors; 

    public House (int streetNumber, String streetName, String lastName) 
    { 
     this.streetNumber = streetNumber; 
     this.streetName = streetName; 
     this.owners = lastName; 
     this.myNeighbors = new HashMap <String, House>(); 
    } 
    public int getStreetNumber() 
    { 
     return streetNumber; 
    } 
    public String getStreetName() 
    { 
     return streetName; 
    } 
    public String getLastName() 
    { 
     return owners; 
    } 
    public void setStreetNumber(int streetNumber) 
    { 
     streetNumber =this.streetNumber; 
    } 
    public void setStreetName(String streetName) 
    { 
     streetName = this.streetName; 
    } 
    public void setLastName(String lastName) 
    { 
     owners = lastName; 
    } 
    public void addNeighbor (String direction, House h) 
    { 
     myNeighbors.put(direction,h); 
    } 
    public House getNeighbor (String direction) 
    { 
     return myNeighbors.get(direction); 
    } 
    public void printAllNeighbors() 
    { 
     for (String key : myNeighbors.keySet()) 
     { 
      System.out.println("\nkey: " + key + " value: " + myNeighbors.get(key)); 
     } 
    } 
    public String toString() 
    { 
     return "Address: " + streetNumber + " " + streetName + "\nOwner: " + owners; 
    } 
    public static void main (String [] args) 
    { 
     House whiteHouse = new House (1600, "Pennsylvania Ave", "Obama"); 
     House jerrysHouse = new House (1602, "Pennsylvania Ave", "Mabrito"); 
     House guentersHouse = new House (1604, "Pennsylvania Ave", "Tusch"); 
     House anasHouse = new House (1609, "Pennsylvania Ave", "Posada"); 

     whiteHouse.addNeighbor("east", jerrysHouse); 
     whiteHouse.addNeighbor("south", guentersHouse); 
     whiteHouse.addNeighbor("north west", anasHouse); 

     System.out.println(whiteHouse);  
     whiteHouse.printAllNeighbors(); 

     System.out.println("****************************** \n" + jerrysHouse); 
     jerrysHouse.printAllNeighbors(); 

     System.out.println("****************************** \n" + guentersHouse); 
     guentersHouse.printAllNeighbors(); 

     System.out.println("****************************** \n" + anasHouse); 
     anasHouse.printAllNeighbors(); 
    } 
}

來源

2015-07-10 06:59:17 Vishnu

HashMap問題，打印鄰居

回答

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