Menene abubuwan da ba za a iya canzawa ba kuma me yasa suke amfani da su?

Question

Accepted Answer

Wani **abu wanda ba za a iya canzawa ba** ba zai iya canza bayan an gina shi — kowane filin an saka jiya, kuma babu wata hanya da ke canza halin. Don "canzawa", ka ƙirƙira sabon abu.

## Gina nau'i wanda ba za a iya canzawa ba

```java
public final class Money {              // final: can't be subclassed to add mutation
    private final int cents;            // final fields, set once
    private final String currency;

public Money(int cents, String currency) {
        this.cents = cents;
        this.currency = currency;
    }

public Money plus(Money other) {    // returns a NEW object, no mutation
        return new Money(this.cents + other.cents, currency);
    }
    public int cents() { return cents; }
}
```

`plus` ba ya canza `this`; yana dawo da sabon `Money`.

## Me yasa ba za a iya canzawa ba yana taimaka

```text
✓ Thread-safe by default → no shared mutable state, no locks needed
✓ Safe to share/cache    → no defensive copies
✓ Valid forever          → if valid at construction, stays valid
✓ Usable as map keys     → hashCode never changes
```

## Ƙankunan

```text
⚠️ Creates new objects on every change → more allocation/GC pressure
⚠️ Awkward for large objects updated frequently (mitigated by builders / persistent
   data structures)
```

Jagora game da *bakin ciki* ba za a iya canzawa ba: filin `final` da ke nuni wa jerin mai yuwuwa shine har yanzu mai yuwuwa ta hanyar haka maƙarƙashin aiki. Kwatance sanin karya ko yi amfani da jerin da ba za a iya canzawa ba.

## Me yasa yake mahimmanci

Ba za a iya canzawa ba yana guje da cikakken kakarinsa: babu wanda zai iya canza abu kusan ka, don haka tunani da gida da ke cikin hade suke saukar sanyin.

Abinda yasa nau'in daraja (jeri, `LocalDate`, rikodin) ba za a iya canzawa ba ne a cikin harsuna na jiya — allaka, ajiyar kujerun, da kuma amfani da mabugi cikin amince ba tare da karya sanin ba.