A Java, Strings fasali ba za su iya canza — da zarar an saki su, batun su ba zai iya canzawa ba. Duk aiki da ya ce ya canza String a gida yana aiki yake saubuwar String. Don canji da canji sannu-sannu da kyau, kafa StringBuilder a maimakon sa.
;
s.concat();
System.out.println(s);
s = s + ;
Hanyoyi kamar concat, toUpperCase, replace da substring duk suna dawo da saubuwa String fasali — na asali ba a canza shi ba.
✓ Thread safety — immutable objects are safe to share across threads (no locking)
✓ String pool — identical string literals can be SHARED/reused (memory savings)
✓ Hashing/keys — safe as HashMap keys (hashCode can be cached, never changes)
✓ Security — strings used for filenames, URLs, credentials can't be altered
after a security check
Rashin canzawa yana sa Strings su cika thread-safe, yana bugi JVM da ya intern (raba) abubuwan rubutu ta hanyar String pool, kuma yana sa su tsarki kamar muni makawa (dusunsunsu ba ya canza ba).
// ❌ creates a NEW string object on EVERY iteration — O(n²), wasteful
String result = "";
for (int i = 0; i < 10000; i++) {
result += i; // each += allocates a whole new string
}
Domin kowane += yana aiki new String (kwafin duk abin da ya gabata), gina Strings a cikin loop shine quadratic kuma yana haifar da gurguzu mai yawa.
// ✅ StringBuilder mutates an internal buffer — O(n), efficient
StringBuilder sb = new StringBuilder();
for (int i = 0; i < 10000; i++) {
sb.append(i); // modifies the buffer in place, no new objects
}
String result = sb.toString(); // convert to a String once, at the end
StringBuilder yanzu fasali ne na haruffa da za a iya canzawa — append/insert/delete suna canza gida na ciki ba tare da abubuwan sabuwa ba, wanda ya sa gina da tushe loop ke zama mabur. (StringBuffer shine zuwa thread-safe amma sannu-sannu.)
Rashin canzawa na Strings shine siffa ta Java da ke da mahimman sakamako: yana ba da kariya thread, yana ba da string pool wanda ke ceton ƙarfi, kuma yana sa su tsarki kamar muni makawa da a cikin yanayin kariya — amma yana nufin kuma cewa haɗin Strings na rashin tunani a cikin loop shine ainihin matsalar aiki (O(n²), gurguzu mai yawa).
Sanin yadda ake amfani da StringBuilder don canji da canji sannu-sannu shine buhaɗi na aiki wanda ya zo kai tsaye daga fahimta rashin canzawa.
Dambar nan — me yaushe Strings suke rashin canzawa (kariya, raba, hashing) da yaushe zabura zuwa StringBuilder (haɗin loop) — shine jiya shaida jarida da gyara aiki a duniya.