问HASHMAP，关键的礼物仍然给出“假”结果
EN

Stack Overflow用户

提问于 2016-11-22 02:10:00

回答 2查看 56关注 0票数 0

下面是我的代码，即使键存在，也返回false：

import java.util.HashMap;
import java.util.Map;
import java.io.BufferedReader;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.IOException;


public class SequenceNumber {

 public static int getSequenceNumber (String TcOrderId){

    // Create a hash map to set key values pair.
    Map<String, Integer> map = new HashMap<String, Integer>();  
    int i= 1;

    // check if hashmap contains the key.
    System.out.println("key present " +map.containsKey(TcOrderId));
    if (map.containsKey(TcOrderId))
    {
       //Key Present
       System.out.println("Inside IF ");
       int value = map.get(TcOrderId);
       System.out.println("value from the key " + value);
       map.remove(value);
       map.put(TcOrderId, value+1);
       return map.get(TcOrderId);
    }
    else
    {
        //Key Not present
        System.out.println("INSIDE ELSE ");
        map.put(TcOrderId, i);
        System.out.println("map "+ map);
        return map.get(TcOrderId);
    }
}

public static void main(String[] args) throws IOException {

    String sCurrentLine;
    BufferedReader br = null;
    try {
        br = new BufferedReader(new FileReader("C:\\Users\\BongAn\\Desktop\\Package\\testing.txt"));
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    {
        while ((sCurrentLine = br.readLine()) != null) {
            //String orderid = sCurrentLine.substring(0, 6);
            System.out.println("reading line " +sCurrentLine);
            int seqvalue = getSequenceNumber(sCurrentLine);
            System.out.println("seqvalue "+seqvalue);
        }

    }

}

}

在文件中输入数据：

1233

1234

结果应该是

但是每次它进入going循环，其结果是

我正在尝试使用HASHMAP，因为我正在创建自己的索引。

java

hashmap

语音识别特惠，低至14.9元！

提供业界非常具有性价比的语音识别服务，超高识别准确率，适用多场景

回答 2

Stack Overflow用户

回答已采纳

发布于 2016-11-22 02:41:11

每次调用getSequenceNumber函数时，都会在代码中创建新的HashMap。我相信这不是你想要的。

为了避免这种情况，您可以简单地将Map<String, Integer> map = new HashMap<String, Integer>();移动到类的主体中。因为函数getSequenceNumber是一个静态函数，所以您需要使变量是静态的。希望这能有所帮助。

片段：

public class SequenceNumber {

 // PUT STATIC VARIABLE HERE:
 static Map<String, Integer> map = new HashMap<String, Integer>();  

 public static int getSequenceNumber (String TcOrderId){

    // Create a hash map to set key values pair.
    // (REMOVE) Map<String, Integer> map = new HashMap<String, Integer>();**  
    int i= 1;

    // check if hashmap contains the key.
  ...
  }
...
}

另一种替代

(也许更好)是避免静态函数和变量，并创建SequenceNumber对象的实例。这样，您就可以将两个不同的实例编号分开保存。

简单片段：

public class SequenceNumber {

 // Your hashmap here:
 Map<String, Integer> map = new HashMap<String, Integer>();

 public int getSequenceNumber (String TcOrderId) {
  // ...
 }

public static void main(String[] args) throws IOException {

    // Instance of SequenceNumber object:
    SequenceNumber sequenceNumber = new SequenceNumber();

    String sCurrentLine;
    BufferedReader br = null;

    // ...
        while ((sCurrentLine = br.readLine()) != null) {
            //String orderid = sCurrentLine.substring(0, 6);
            System.out.println("reading line " +sCurrentLine);
            int seqvalue = sequenceNumber.getSequenceNumber(sCurrentLine);
            System.out.println("seqvalue "+seqvalue);
        }
    // ...
    }
}

票数 0

Stack Overflow用户

发布于 2016-11-22 02:25:58

像这样的东西应该管用。不过还没试过运行。

public class SequenceNumber {

 public static int getSequenceNumber (String TcOrderId, Map<String, Integer> map){  
    if(!map.contains(TcOrderId)){
        map.put(TcOrderId, 0);
    }

    map.put(TcOrderId, map.get(TcOrderId)+1);
    return map.get(TcOrderId);
}

public static void main(String[] args) throws IOException {

    String sCurrentLine;
    BufferedReader br = null;
    Map<String, Integer> map = new HashMap<String, Integer>();
    try {
        br = new BufferedReader(new FileReader("C:\\Users\\BongAn\\Desktop\\Package\\testing.txt"));
    } catch (FileNotFoundException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
    {
        while ((sCurrentLine = br.readLine()) != null) {
            //String orderid = sCurrentLine.substring(0, 6);
            System.out.println("reading line " +sCurrentLine);
            int seqvalue = getSequenceNumber(sCurrentLine, map);
            System.out.println("seqvalue "+seqvalue);
        }

    }