✏️ Explanatory Question

[Operation on File]

Question:

What is the difference between the following two statements? 

1. FileWriter fw = new FileWriter();

2. FileWriter fw = new FileWriter(, true);

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📘 Detailed Answer
🟢 Easy
← Previous [Recursion] Question: A student has written the following code. It is written to check whether a string is palindrome or not. However, the code is not giving the desired result when the parameter “MADAM” is passed to the method isPalindrome(). Analyse the code and find out the logical error. public class PalindromeTesting { public static boolean isPalindrome(String word) { if(word.length() < 1) { return true; } else if(word.charAt(0) != word.charAt(word.length() - 1)) { return false; } else { return isPalindrome(word.substring(0, word.length() - 1)); } } }
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Answer with Explanation

Answer:

Statement 1:

FileWriter fw = new FileWriter();

This statement opens the file in overwrite mode.

  • If the file already contains data, the old data will be erased.
  • New data will be written from the beginning of the file.

Statement 2:

FileWriter fw = new FileWriter(, true);

This statement opens the file in append mode.

  • Existing data in the file remains unchanged.
  • New data is added at the end of the file.

Explanation:

The second parameter: 

true

indicates: 

Append Mode

If this parameter is absent, Java uses: 

Overwrite Mode

Example:

Suppose the file contains: 

Hello

Using Statement 1:

fw.write("Java");

Final file content: 

Java

Old data is removed.

Using Statement 2:

fw.write("Java");

Final file content: 

HelloJava

New data is appended at the end.

Conclusion:

  • FileWriter(file) → Overwrites existing data
  • FileWriter(file, true) → Appends new data
← Previous [Recursion] Question: A student has written the following code. It is written to check whether a string is palindrome or not. However, the code is not giving the desired result when the parameter “MADAM” is passed to the method isPalindrome(). Analyse the code and find out the logical error. public class PalindromeTesting { public static boolean isPalindrome(String word) { if(word.length() < 1) { return true; } else if(word.charAt(0) != word.charAt(word.length() - 1)) { return false; } else { return isPalindrome(word.substring(0, word.length() - 1)); } } }