Java HashMap迭代未顯示鍵和變量之間的比較

Question

我試圖通過HashMap進行迭代，並且當檢測到重復的鍵（key = node coord）時，我想給具有相同key（coord）的新節點相同的nodeID（Hasmap value）。 這是我的問題代碼塊和輸出。 如您所見，它輸出key（keys）和新key（finishedLine3）具有相同的值，但是不會進入“ if”語句並更改nodeID。

歷史記錄：我在這里與“ ==”進行比較，但也嘗試過if（keys.equal（finishedLine3））並獲得相同的結果。

我還在輸出中顯示節點鍵：-86.88642133.035899節點值：00000001和節點鍵：-86.88642133.035899節點值：00000010是相同的，但是在迭代過程中，我的邏輯沒有允許對這兩個精確的比較鍵進入我的“ if”塊。

這是我的代碼：

    package com.KatsProject.net;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.text.DecimalFormat;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Set;
public class MakeFile {
    public static void main(String[] args) throws IOException {
         DecimalFormat df = new DecimalFormat("00000000");
         Integer numWords = 0;
         Integer numLines = 1;
         Integer numNodes =0;
         Integer nodeID =0;
         Integer counter=0;
         String nodesID2 ="";
         String newNodeID="";
         String  header = "road_id      #_of_nodes          node_id         node_x_coord        node_y_coord    ... end of list";
         String finishedLine1 = " ";
         String finishedLine2 = " ";
         String finishedLine3 = " ";
         String finishedLine34 = " ";
         String finishedLine = " ";
         String roadID= "";
         String roadID2= "";
         String match=" ";
         String match2=" ";
         String temp=" ";
         BufferedReader br= null;
         BufferedWriter bw= null;
         HashMap<String, String> nodes = new HashMap<String, String>();
         br = new BufferedReader(new FileReader("C:\\Users\\gary\\Desktop\\roads.txt"));
         try {
                bw = new BufferedWriter(new FileWriter("C:\\Users\\gary\\Desktop\\Secretfile"));
            } catch (IOException e) {
                System.out.println("Error writing file");
                e.printStackTrace();
            }
         String line = null;
         while( (line = br.readLine())!= null )
         {   
            if(numLines > 1){
            numWords =0;  
            nodeID +=1; 
            newNodeID= df.format(nodeID);
            nodesID2 = newNodeID;
            String [] tokens = line.split("\\s+");
            roadID = tokens[0]; // save roadID for comparison
            finishedLine1="";
              for(String s :tokens){
                  numWords+=1; 
                  if(numWords == 1){
                     // x.setRoadID(roadID);
                  }  
                  if(numWords ==2 ){
                     match += s;
                  }
                  if(numWords ==3 ){
                      match2 += s;
                      //System.out.println(match2+"this is match2 ,  " + match + "  this is match");
                  }
                  if(numWords == 4 ){
                      finishedLine3 += s;               //for hash table
                      finishedLine3.trim();
                      finishedLine1 += s;
                      finishedLine1 += "      ";
                      //System.out.println(x.getX_coord()+ "   this is x_coord.");
                  }
                  if(numWords == 5){
                      finishedLine3 += s;                 //for hash table
                      finishedLine3.trim();
                      finishedLine1 += s;
                      finishedLine1 += "      ";
                      String key =finishedLine3;
                      //System.out.println("It is    " + nodes.containsKey(key)+ "  that the nodeID for the key :    "+ finishedLine3 + "    is:     " + nodes.get(key)+ "      "+ key );
                      //System.out.println(finishedLine3+ " Is this the line that also includes the roadID #?");
                      //nodes.put(key,newNodeID );
                      Set<String> keySet = nodes.keySet();
                      Iterator<String> keyIterator = keySet.iterator();
                      //System.out.println("Another iteration starts , this is iteration :       "+ nodeID);
                      bw.write("Another iteration starts , this is iteration :       "+ nodeID);
                      bw.write("\n");
                      while (keyIterator.hasNext()) {
                          String keys = keyIterator.next();
                          //System.out.println( keys);
                          //System.out.println(" nodes key: " + keys + " nodes value: " + nodes.get(keys));
                          //System.out.println("Is keys:  "+keys + " equal to finishedLine3 :  " +finishedLine3);
                          if (keys.equals(finishedLine3))
                          {

                              //System.out.println( "This is finishedLine3 :  "+finishedLine3 +" , and it is equal to:  " + keys);  
                              newNodeID = nodes.get(keys);
                              // System.out.println(nodes.get(key) + "     this is nodes.get(key) ");
                              //System.out.println(nodes.get(keys) + "     this is nodes.get(keys) ");
                              //finishedLine2+=nodes.get(finishedLine3);
                              finishedLine3="";
                              }
                      }
                      nodes.put(key,newNodeID );
                      match2="";
                      match="";

                   }
              }
              if ((!(roadID.equals(roadID2)))&&(match.equals(match2)))
              {
                   finishedLine+= roadID;
                   finishedLine+= "              ";
                   finishedLine+=numNodes;
                   finishedLine+= "             ";
                   finishedLine+=finishedLine2;
                   finishedLine+="...end of list \n";
                   bw.write(finishedLine);
                   bw.write("\n");
                   finishedLine=" ";
                   finishedLine2=" ";
                   finishedLine3=" ";
                   numNodes=0;
                   roadID2 = roadID;
                   //roadID2 = x.roadID;
                   match="";
                   match2="";

              }
              if((roadID.equals(roadID2))||roadID2==""){
                  //finishedLine2+= x.getNodeID();
                  finishedLine2+= newNodeID;
                  //System.out.println( " This is finishedLine2 after inserting newNodeID: "+ newNodeID+"   "+ finishedLine2);
                  //System.out.println(newNodeID + "     this is newNodeID copied to finishedLine2 string."+finishedLine2+" checking to see if newNOdeID was changed in string");
                  //System.out.println(" This is finishedLine1: " +finishedLine1);
                  finishedLine2+="          ";
                  finishedLine2 += finishedLine1;
                  finishedLine2+="              ";
                  //System.out.println( " This is finishedLine2: "+ finishedLine2);
                  numNodes+=1;
                  finishedLine1="";
                  match2="";
                  match="";
                  //System.out.println("this is in if statement");
              }
              finishedLine3 = "";
         }
         else{
              System.out.print(header+"\n");
               bw.write(header + "\n");
               numLines+=1;
          }
          roadID2 = roadID;
          match="";
          match2="";

       }    
       br.close(); 
    }    

}

這是我的輸出：

        road_id     #_of_nodes          node_id         node_x_coord        node_y_coord    ... end of list
This is keys:   -86.88642133.035899and this is the :  1  iteration through the while loop
Is keys:   -86.88642133.035899 equal to finishedLine3 :  -86.88651833.035997? 
This is keys:   -86.88642133.035899and this is the :  2  iteration through the while loop
Is keys:   -86.88642133.035899 equal to finishedLine3 :  -86.88657833.03605? 
This is keys:  -86.88651833.035997and this is the :  3  iteration through the while loop
Is keys:  -86.88651833.035997 equal to finishedLine3 :  -86.88657833.03605? 
This is keys:   -86.88642133.035899and this is the :  4  iteration through the while loop
Is keys:   -86.88642133.035899 equal to finishedLine3 :  -86.88666833.03609? 
This is keys:  -86.88651833.035997and this is the :  5  iteration through the while loop
Is keys:  -86.88651833.035997 equal to finishedLine3 :  -86.88666833.03609? 
This is keys:  -86.88657833.03605and this is the :  6  iteration through the while loop
Is keys:  -86.88657833.03605 equal to finishedLine3 :  -86.88666833.03609? 
This is keys:   -86.88642133.035899and this is the :  7  iteration through the while loop
Is keys:   -86.88642133.035899 equal to finishedLine3 :  -86.88674233.03608? 
This is keys:  -86.88651833.035997and this is the :  8  iteration through the while loop
Is keys:  -86.88651833.035997 equal to finishedLine3 :  -86.88674233.03608? 
This is keys:  -86.88666833.03609and this is the :  9  iteration through the while loop
Is keys:  -86.88666833.03609 equal to finishedLine3 :  -86.88674233.03608? 
This is keys:  -86.88657833.03605and this is the :  10  iteration through the while loop
Is keys:  -86.88657833.03605 equal to finishedLine3 :  -86.88674233.03608? 
This is keys:   -86.88642133.035899and this is the :  11  iteration through the while loop
Is keys:   -86.88642133.035899 equal to finishedLine3 :  -86.88679433.036037? 
This is keys:  -86.88651833.035997and this is the :  12  iteration through the while loop
Is keys:  -86.88651833.035997 equal to finishedLine3 :  -86.88679433.036037? 
This is keys:  -86.88674233.03608and this is the :  13  iteration through the while loop
Is keys:  -86.88674233.03608 equal to finishedLine3 :  -86.88679433.036037? 
This is keys:  -86.88666833.03609and this is the :  14  iteration through the while loop
Is keys:  -86.88666833.03609 equal to finishedLine3 :  -86.88679433.036037? 
This is keys:  -86.88657833.03605and this is the :  15  iteration through the while loop
Is keys:  -86.88657833.03605 equal to finishedLine3 :  -86.88679433.036037? 
This is keys:   -86.88642133.035899and this is the :  16  iteration through the while loop
Is keys:   -86.88642133.035899 equal to finishedLine3 :  -86.88679133.035966? 
This is keys:  -86.88651833.035997and this is the :  17  iteration through the while loop
Is keys:  -86.88651833.035997 equal to finishedLine3 :  -86.88679133.035966? 
This is keys:  -86.88674233.03608and this is the :  18  iteration through the while loop
Is keys:  -86.88674233.03608 equal to finishedLine3 :  -86.88679133.035966? 
This is keys:  -86.88679433.036037and this is the :  19  iteration through the while loop
Is keys:  -86.88679433.036037 equal to finishedLine3 :  -86.88679133.035966? 
This is keys:  -86.88666833.03609and this is the :  20  iteration through the while loop
Is keys:  -86.88666833.03609 equal to finishedLine3 :  -86.88679133.035966? 
This is keys:  -86.88657833.03605and this is the :  21  iteration through the while loop
Is keys:  -86.88657833.03605 equal to finishedLine3 :  -86.88679133.035966? 
This is keys:   -86.88642133.035899and this is the :  22  iteration through the while loop
Is keys:   -86.88642133.035899 equal to finishedLine3 :  -86.88674333.03591? 
This is keys:  -86.88651833.035997and this is the :  23  iteration through the while loop
Is keys:  -86.88651833.035997 equal to finishedLine3 :  -86.88674333.03591? 
This is keys:  -86.88679133.035966and this is the :  24  iteration through the while loop
Is keys:  -86.88679133.035966 equal to finishedLine3 :  -86.88674333.03591? 
This is keys:  -86.88674233.03608and this is the :  25  iteration through the while loop
Is keys:  -86.88674233.03608 equal to finishedLine3 :  -86.88674333.03591? 
This is keys:  -86.88679433.036037and this is the :  26  iteration through the while loop
Is keys:  -86.88679433.036037 equal to finishedLine3 :  -86.88674333.03591? 
This is keys:  -86.88666833.03609and this is the :  27  iteration through the while loop
Is keys:  -86.88666833.03609 equal to finishedLine3 :  -86.88674333.03591? 
This is keys:  -86.88657833.03605and this is the :  28  iteration through the while loop
Is keys:  -86.88657833.03605 equal to finishedLine3 :  -86.88674333.03591? 
This is keys:   -86.88642133.035899and this is the :  29  iteration through the while loop
Is keys:   -86.88642133.035899 equal to finishedLine3 :  -86.88668133.035885? 
This is keys:  -86.88651833.035997and this is the :  30  iteration through the while loop
Is keys:  -86.88651833.035997 equal to finishedLine3 :  -86.88668133.035885? 
This is keys:  -86.88674333.03591and this is the :  31  iteration through the while loop
Is keys:  -86.88674333.03591 equal to finishedLine3 :  -86.88668133.035885? 
This is keys:  -86.88679133.035966and this is the :  32  iteration through the while loop
Is keys:  -86.88679133.035966 equal to finishedLine3 :  -86.88668133.035885? 
This is keys:  -86.88674233.03608and this is the :  33  iteration through the while loop
Is keys:  -86.88674233.03608 equal to finishedLine3 :  -86.88668133.035885? 
This is keys:  -86.88679433.036037and this is the :  34  iteration through the while loop
Is keys:  -86.88679433.036037 equal to finishedLine3 :  -86.88668133.035885? 
This is keys:  -86.88666833.03609and this is the :  35  iteration through the while loop
Is keys:  -86.88666833.03609 equal to finishedLine3 :  -86.88668133.035885? 
This is keys:  -86.88657833.03605and this is the :  36  iteration through the while loop
Is keys:  -86.88657833.03605 equal to finishedLine3 :  -86.88668133.035885? 
This is keys:   -86.88642133.035899and this is the :  37  iteration through the while loop
Is keys:   -86.88642133.035899 equal to finishedLine3 :  -86.88642133.035899? 

感謝任何能夠提供幫助並希望我足夠清楚和簡潔的人。

Answer 1

使用== ，通常意味着對象是相同的。 因此，避免對對象使用==來支持Object equals()而對基本類型使用== 。 在您的情況下，應使用keys.equals(finishedLine3)因為這是兩個不同的對象。 在上面你的問題，你有沒有表現出的初始化finishedLine3這可能是導致錯誤的行為。

Answer 2

我假設您復制了已運行的代碼的輸出。 我建議您在比較兩個字符串對象時使用Object equals（）。 但是我可以在您的代碼中看到的是，您的密鑰中有一個前導空格（“ -86.88642133.035899”而不是“ -86.88642133.035899”）。 因此，您可以在創建HashMap時嘗試避免這種情況，或者如果您從某個文件中獲取輸入，則可以修剪字符串，這是指向文檔的鏈接-

https://docs.oracle.com/javase/7/docs/api/java/lang/String.html#trim（）

希望這可以幫助。