In Java, strings are widely used to store and manipulate text. However, when it comes to handling sensitive information—like passwords, credit card numbers, or tokens—using strings poses serious security risks. Strings are immutable and stored in memory until garbage collected, which makes them prone to memory leaks, unauthorized access, or reverse engineering.
This tutorial covers string security practices in Java: how to properly handle sensitive data, avoid common vulnerabilities, and secure your applications from memory-based attacks.
🛡️ Why Strings Are a Security Risk
Java String is immutable and stored in memory until garbage collected. Sensitive data stored in a string:
- Cannot be manually wiped
- May live in memory longer than intended
- Could be exposed via memory dumps, heap analysis, or thread inspection
Example: Risk with String Password
String password = "mySecret123"; // cannot be erased manually
🔐 Secure Alternative: char[]
Use char[] for passwords and sensitive data so you can overwrite the contents once done.
✅ Secure Way
char[] password = {'m','y','S','e','c','r','e','t'};
Arrays.fill(password, '