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How to Reverse a String in Java?

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How to Reverse a String in Java?

How to Reverse a String ? is about working with text in Java. Remember the base rule first: String is immutable. Compare content with equals, not ==.

For How to Reverse a String ?, common APIs from memory: length(), charAt(i), substring(start, end), contains, equalsIgnoreCase, toUpperCase. Index starts at 0.

If How to Reverse a String ? 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 How to Reverse a String ?, 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. How to Reverse a String in Java? — stringBuilder.reverse is a clean way to reverse text. Start from main, go line by line, and stop at each print. That output is the proof for How to Reverse a String ?.

Exam tip

== vs equals() on String is a classic trap.

Example

public class Main {
  public static void main(String[] args) {
    String s = "Java";
    String rev = new StringBuilder(s).reverse().toString();
    System.out.println(rev); // avaJ
  }
}

How to Reverse a String in Java? — stringBuilder.reverse is a clean way to reverse text.

Short notes

DefHow to Reverse a String ? works with Java text. String itself is immutable.
RuleHow to Reverse a String ? — compare content with equals, not ==.
RememberHow to Reverse a String ? — length, charAt, substring. substring end index is exclusive.
TrapHow to Reverse a String ? — == compares references. User input almost never matches with ==.

Java · Theory

How to Reverse a String in Java?

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Theory

87/270

How to Reverse a String in Java?

How to Reverse a String ? is about working with text in Java. Remember the base rule first: String is immutable. Compare content with equals, not ==.

For How to Reverse a String ?, common APIs from memory: length(), charAt(i), substring(start, end), contains, equalsIgnoreCase, toUpperCase. Index starts at 0.

If How to Reverse a String ? 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 How to Reverse a String ?, say the output before you code. Off-by-one on substring is a common trap (end index is exclusive).

Exam tip

== vs equals() on String is a classic trap.

Example

public class Main {
  public static void main(String[] args) {
    String s = "Java";
    String rev = new StringBuilder(s).reverse().toString();
    System.out.println(rev); // avaJ
  }
}

How to Reverse a String in Java? — stringBuilder.reverse is a clean way to reverse text.

Short notes

DefHow to Reverse a String ? works with Java text. String itself is immutable.
RuleHow to Reverse a String ? — compare content with equals, not ==.
RememberHow to Reverse a String ? — length, charAt, substring. substring end index is exclusive.
TrapHow to Reverse a String ? — == compares references. User input almost never matches with ==.

How to Reverse a String in Java?

Example

Short notes

Questions

How to Reverse a String in Java?

Example

Short notes

Questions