How Java String Constants Are Stored Inside .class Files

A visual deep-dive into how string constants are encoded in the Java constant pool — CONSTANT_Utf8, CONSTANT_String, and the ldc instruction — with hex diagrams and patching examples.

The Constant Pool

CONSTANT_Utf8 (tag = 1)

CONSTANT_String (tag = 8)

The ldc Instruction

Patching a String: Step by Step

What About Different Lengths?

Same-Length Edits Are Still Safest

Modified UTF-8: One Subtlety

Strings That Appear Multiple Times

Practical Example: Patching a Config String