In Java (String references and reassignment), what does this program print? public class StringRef { public static void main(String [] args) { String s1 = "abc"; String s2 = "def"; String s3 = s2; /* Line 7 */ s2 = "ghi"; System.out.println(s1 + s2 + s3); } }

Introduction / Context:
The question demonstrates how Java variable assignment with immutable Strings copies references, not contents, and how later reassignment of one reference does not change the object referenced by another variable captured earlier.

Given Data / Assumptions:

• s1 starts as "abc".
• s2 starts as "def".
• s3 = s2 means both refer to the same "def" at that moment.
• s2 = "ghi" rebinds s2 to a new String; s3 still refers to "def".

Concept / Approach:
Java Strings are immutable; assignment does not clone data. Reassigning s2 changes only which object s2 points to. The original object "def" remains, and s3 still points to it.

Step-by-Step Solution:

Verification / Alternative check:
If we had modified contents (which is impossible with immutable Strings), only then would s3 reflect such changes. With mutable types (e.g., StringBuilder), sharing a reference and then mutating would affect all aliases.

Why Other Options Are Wrong:

• "abcdefghi": presumes concatenation in original order without reassignment.
• "abcdefdef": assumes s2 did not change.
• "abcghighi": assumes s3 also changed to "ghi".

Common Pitfalls:
Assuming Java reassignments perform deep copies; they do not. Variables hold references to objects.

Final Answer:
abcghidef