The variable satisfy the condition of if,but the result show don't satisfy all the time

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The variable lastTagPair always equal null. The editor is utf-8, the file reader is also utf-8, obviously the if statement is satisfied, but the code in if statement was never executed.

 public static HashMap<String, String> fileRead(){
     HashMap<String, String> dummy_tagPairSentences = new HashMap<String, String>();
     try {
         String encoding="UTF-8";
         File file=new File("entityLinkiingResult3.txt");
         if(file.isFile() && file.exists()){ //
             InputStreamReader read = new InputStreamReader(
             new FileInputStream(file),encoding);//
             BufferedReader bufferedReader = new BufferedReader(read);

             String lineTxt = null; 
             String lastTagPair = null;
             String candidateSentences = null; 
             String dummy_title = null; 
             String tagPair = null;

             while((lineTxt = bufferedReader.readLine()) != null){

                 if (lineTxt.length() >= 8){
                     dummy_title = lineTxt.substring(0,7); 
                     tagPair = lineTxt.substring(8);
                     //System.out.println(dummy_title + " " + tagPair);
                    }
                 else{ 
                   }

                 if (dummy_title == "TagPair"){
                     dummy_tagPairSentences.put(lastTagPair,candidateSentences);    
                     System.out.println(lastTagPair + candidateSentences); 
                     System.out.println("?");  
                     lastTagPair = tagPair;
                     candidateSentences = null;
                   }      
                   else
                   { 
                       candidateSentences += lineTxt + "\n";                          
                   }                         
             }
             read.close();
 }else{
     System.out.println;
 }
 } catch (Exception e) {
     System.out.println;
     e.printStackTrace();
 } 
return dummy_tagPairSentences;
}