兩個用戶輸入是不同的，但程序識別它們相同

Question

我正在創建一個程序，稍後將兩個文件比較在一起。我創建了兩個while循環來檢查用戶輸入的文件是否是正確的文件類型，是否有正確的路徑，並且是正常的文件。第一個while循環檢查第一個輸入文件（稱爲initialFile），第二個while循環檢查第二個輸入文件（稱爲compareFile）。第二個while循環檢查還會檢查以確保comparefile與initialFile不同。

我正在運行的問題是當我測試第二個while循環檢查是否捕獲到相同的文件類型輸入時。如果文件類型錯誤，沒有一個有效的文件路徑，或者如果它不是一個普通的文件，但如果我輸入的文件與compareFile相同，initialFile while循環結束當它應該循環。

下面是相關代碼：

import java.util.Scanner; 
import java.io.File; 
import java.lang.Exception; 
import java.io.FileNotFoundException; 


public class QuickSortAnagram { 


    public static void main(String[] args) { 

    Scanner scnr = new Scanner(System.in); 

    String initialInput = " "; 

    String compareInput = " "; 

    //Check to make sure FIRST user input is the correct file type, is a valid file pathway, and is a normal file 

    /*while loop requires user to input a String that ends with ".txt" before 
    *the loop will end. This ensures that the user will input a String 
    *that represents the correct file type before being allowed to move on. 
    The while loop also requires that the user input a filename that has 
    a valid pathway to it and is a normal file or the user will not be allowed to move on*/ 

    boolean initialWhileLoopEnd = false; 

    while(initialWhileLoopEnd == false) { 

    System.out.println("Enter initial test file (Please make sure it is in the form 'textfile.txt', that there is a valid pathway to file, and that file is normal or program will not be able to continue): "); 
    initialInput = scnr.next(); 

    File initialFile = new File(initialInput); 

    if(initialInput.endsWith(".txt")) { 
     if(initialFile.isFile()) { 
     initialWhileLoopEnd = true; 
     } 
     else { 
     System.out.println("File does not exist and/or is not a normal file"); 
     } 
     } 
    else { 
    System.out.println("Invalid file type"); 
    } 
    } 

    //initializes file outside of while loop so it can be read later 
    File initialFile = new File(initialInput); 


    //Check to make sure SECOND user input is the correct file type, is a valid file pathway, is a normal file, and is not the same file name that user used for the FIRST check 

    /*while loop requires user to input a String that ends with ".txt" before 
    *the loop will end. This ensures that the user will input a String 
    *that represents the correct file type before being allowed to move on. 
    The while loop also requires that the user input a filename that has 
    a valid pathway to it and is a normal file or the user will not be allowed to move on*/ 

    boolean compareWhileLoopEnd = false; 

    while(compareWhileLoopEnd == false) { 

    System.out.println("Enter compare test file (Please make sure it is in the form 'textfile.txt', that there is a valid pathway to file, that file is normal, and that file is not identical to the initial file inputed or program will not be able to continue): "); 
    compareInput = scnr.next(); 

    File compareFile = new File(compareInput); 

    if(compareInput.endsWith(".txt")) { 
     if(compareFile.isFile()) { 
     if(compareFile != initialFile) { 
     compareWhileLoopEnd = true; 
     } 
     else { 
      System.out.println("File is identical to the initial file inputed. Please input a different file"); 
     } 
     } 
     else { 
     System.out.println("File does not exist and/or is not a normal file"); 
     } 
     } 
    else { 
    System.out.println("Invalid file type"); 
    } 
    } 

    File compareFile = new File(compareInput); 

    scnr.close(); 
    } 
} 

爲什麼當它應該循環我while循環結束？

Answer 1

那麼，就看看你的代碼：

if (compareFile != initialFile) { 
    compareWhileLoopEnd = true; 
} 

所以，如果第二個文件的對象是不一樣的對象作爲第一個文件對象（這是總是的情況下），則結束循環。

應該改爲

if (compareFile.equals(initialFile)) { 
    System.out.println("File is identical to the initial file inputed. Please input a different file"); } 
else { 
    compareWhileLoopEnd = true; 
} 

注意，即使上面的代碼，它不是完全正確的，因爲第一個文件可能是foo.txt和第二可能是../currentDirectory/foo.txt，這不會是平等的，但它們實際上是指文件系統上的相同文件。如果您想要捕捉這些問題，請查看File的javadoc，並瞭解如何獲取文件的絕對路徑。