Piye carane panganan njejokan lan bedane checked/unchecked?

Question

IT Interview Practice · Accepted Answer

Java nangani kesalahan karo **`try`/`catch`/`finally`**, lan unikno mbedake **panganan checked** (kudu dinyatakake utawa ditangani) saka **panganan unchecked** (runtime, ora dipeksa). Kapaham bedane iki minangka tengah-tengahing panganan kesalahan Java.

## Struktur dhasar

```java
try {
    FileReader f = new FileReader("file.txt");   // may throw IOException
    // ... use it ...
} catch (FileNotFoundException e) {
    System.out.println("not found: " + e.getMessage()); // specific first
} catch (IOException e) {
    System.out.println("io error");                      // broader after
} finally {
    System.out.println("always runs — cleanup");         // runs no matter what
}
```

`finally` tansah dijalanaken (bebersihan), sanajan panganan dilebokake utawa `return` dumadi.

## Hierarki panganan

```text
Throwable
  ├── Error            — serious JVM problems (OutOfMemoryError) — don't catch
  └── Exception
        ├── RuntimeException  → UNCHECKED (not enforced by the compiler)
        │     NullPointerException, IllegalArgumentException, IndexOutOfBounds...
        └── (other Exceptions) → CHECKED (compiler enforces handling)
              IOException, SQLException...
```

## Panganan checked — dipeksa dening compiler

```java
// MUST either catch it or declare `throws` — the compiler won't let you ignore it
public void readFile() throws IOException {   // declare it
    Files.readAllLines(Paths.get("file.txt")); // throws checked IOException
}
```

Panganan **checked** (IOException, SQLException) makili kahanan sing bisa dipulih, kaandele (file ilang, gagal jaringan). Compiler *memaksa* sampeyan nangani utawa dinyatakake — nggawe panganan gagal eksternal gamblang.

## Panganan unchecked — runtime, ora dipeksa

```java
// NOT required to declare or catch — usually indicate PROGRAMMING BUGS
String s = null;
s.length();                       // NullPointerException (unchecked)
int x = arr[10];                   // ArrayIndexOutOfBoundsException (unchecked)
Integer.parseInt("abc");           // NumberFormatException (unchecked)
```

Panganan **unchecked** (subclass RuntimeException) biasane tandha kesalahan program — sira ngamandake bug tinimbang nangani ing sadurunge. Compiler ora memaksa panganan.

## try-with-resources (bebersihan otomatis)

```java
// resources implementing AutoCloseable are closed automatically
try (FileReader f = new FileReader("file.txt")) {
    // use f
}   // f.close() called automatically, even on exception — no finally needed
```

## Laku becik

```text
✓ Catch specific exceptions, not bare Exception
✓ Use try-with-resources for files/connections (auto-close)
✓ Don't swallow exceptions silently (empty catch blocks)
✓ Throw meaningful exceptions; include context in messages
✓ Custom exceptions extend Exception (checked) or RuntimeException (unchecked)
```

## Piyenapa kulawargan

Panganan kesalahan sing kuat kudu diperlokake, lan **bedane checked/unchecked Java minangka fitur (lan kapengin diperdebatake)** sing perlu dikapaham kanthi jembar.

Panganan checked memaksa panganan gamblang gagal eksternal kaandele (I/O, DB) — ningkatake kapercayan nanging kadhang dikritik minangka ramet; panganan unchecked makili bug sing kudu didandani tinimbang ditangani.Ngerti hierarki, bisokna saben jinis, semantik `try/catch/finally`, lan **try-with-resources** modern kanggo bebersihan otomatis minangka dhasar kanggo nulis Java sing bener lan kapercayan — lan kanggo ngrumusake panganan dhewe kanthi bener.

Bedane membentuk cara API Java dirancang lan minangka ginem sing kerep ana ing wawancara lan ulasan kode.

Struktur dhasar

Hierarki panganan

Panganan checked — dipeksa dening compiler

Panganan unchecked — runtime, ora dipeksa

try-with-resources (bebersihan otomatis)

Laku becik

Piyenapa kulawargan

Pitakon sing gegandhengan