Ni lini gani unapaswa kutumia getters na setters (na lini si)?

Question

Accepted Answer

Getters/setters hufichula upatikanaji uliosimamiwa wa sehemu, lakini matokeo ya kawaida ya kuongeza mmoja *kwa kila sehemu* ni muundo mbaya. Swali halisi ni: je getter/setter inaongeza thamani, au inajaza upya uwanja wa umma na hatua za ziada?

## Wakati setter inahitajika

```java
public class Thermostat {
    private int target;
    public void setTarget(int t) {     // setter adds VALIDATION
        if (t < 5 || t > 30)
            throw new IllegalArgumentException("out of range");
        this.target = t;
    }
    public int getTarget() { return target; }
}
```

Hapa setter inatumia invariant — inastahili.

## Wakati wanaojua tu kelele

```java
// Anti-pattern: "encapsulation theatre"
public class Point {
    private int x, y;
    public int getX() { return x; }    public void setX(int x){ this.x=x; }
    public int getY() { return y; }    public void setY(int y){ this.y=y; }
}
// This is no safer than public fields — and now x,y can change anytime.
```

## Mfumo bora: ambia, usiwale

Badala ya kufichula hali kwa ajili ya wanaoita kugeuzana, fichula *tabia*:

```java
account.withdraw(100);          // ✅ behavior protects the rule
// vs
account.setBalance(account.getBalance() - 100);  // ❌ logic leaks to caller
```

## Kwa nini inashangilia

Setter kwenye kila sehemu ni karibu sawa na kufanya sehemu kuwa ya umma — inatoa hisi ya uwongo wa uproteksho wakati inakuruhusu mtu yeyote anayeita kugeuza hali kwa uhuru.

Kuundwa kuzunguka tabia ("ambia, usiwale") inashikilia invariants ndani ya kitu, inapunguza mkutano na mara nyingi inafichua kwamba nyingi za sehemu zinapaswa kuwa kinyume bila setter kabisa.