Java toString method — Java Technical Interview Questions & Answers

Java toString method

Java toString method

  • toString method is about working with text in Java. Remember the base rule first: String is immutable. Compare content with equals, not ==.
  • For toString method, common APIs from memory: length(), charAt(i), substring(start, end), contains, equalsIgnoreCase, toUpperCase. Index starts at 0.
  • If toString method is StringBuilder/StringBuffer, you change text in place with append. If it is comparison, show == false and equals true for two new String("Hi").
  • For toString method, say the output before you code. Off-by-one on substring is a common trap (end index is exclusive).
  • Let's take this on the board with one tiny Main class — no extra files. Java toString method — shows length, substring, case change, and equalsIgnoreCase. Start from main, go line by line, and stop at each print. That output is the proof for toString method.

Technical Interview Tip: == vs equals() on String is a classic trap.

Code Examples for Java toString method

Example

// String methods
public class Main {
  public static void main(String[] args) {
    String s = "PrepPilot";
    System.out.println(s.length());
    System.out.println(s.substring(0, 4));
    System.out.println(s.toUpperCase());
    System.out.println("prep".equalsIgnoreCase("PREP"));
  }
}

Java toString method — shows length, substring, case change, and equalsIgnoreCase.

How to Explain Java toString method to an Interviewer

What is toString method?

toString method works with Java text. String itself is immutable. toString method — compare content with equals, not ==. toString method — length, charAt, substring. substring end index is exclusive.

Why do we use toString method in Java?

Makes the program clearer or safer toString method works with Java text. String itself is immutable.

Write one small example of toString method.

Show syntax Say what prints

What mistake do beginners make with toString method?

Only the name, no example toString method — == compares references. User input almost never matches with ==.

Where is toString method used in a real program?

Day-to-day Java code