Convert String to int in Java

🚀 Mastering Java String to int Conversion (The Fun Way!)

Ever found yourself staring at a String and wishing it could magically transform into an int? Well, Java’s got your back! Let's dive into the world of number conversions and make it a fun ride. 🎢

1️⃣ Using Integer.parseInt() (The Classic Way)

📝 Syntax

Integer.parseInt() is like your reliable friend who always gets the job done. It takes a String, chews it up (figuratively, of course), and spits out an int.

It comes in three flavors:

public static int parseInt(String s) throws NumberFormatException { ... }
public static int parseInt(String s, int radix) throws NumberFormatException { ... }
public static int parseInt(String s, int beginIndex, int endIndex, int radix) throws NumberFormatException { ... }

✨ Example Magic

Let’s turn some strings into integers like a Java wizard. 🧙‍♂️

Assertions.assertEquals(1001, Integer.parseInt("1001"));
Assertions.assertEquals(513, Integer.parseInt("1001", 8));
Assertions.assertEquals(1001, Integer.parseInt("amount=1001", 7, 11, 10));

Cool, right? But wait—there’s a catch! 🚨

❌ Beware of NumberFormatException

Java is great, but it won't let you fool around with invalid numbers. If you try to pass nonsense, it'll throw a tantrum! 😡

Assertions.assertThrows(NumberFormatException.class, () -> {
  Integer.parseInt(null);
});

Assertions.assertThrows(NumberFormatException.class, () -> {
  Integer.parseInt("abc");
});

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2️⃣ Using Integer.valueOf() (The Cousin of parseInt())

Integer.valueOf() is basically parseInt(), but it returns an Integer object instead of a primitive int. So, it’s fancier. 🎩

public static Integer valueOf(String s) throws NumberFormatException {...}
public static Integer valueOf(String s, int radix) throws NumberFormatException {...}

🔥 Example Fireworks

Assertions.assertEquals(1001, Integer.valueOf("1001"));
Assertions.assertEquals(513, Integer.valueOf("1001", 8));

Oops, don't mess up the input! 🚨

Assertions.assertThrows(NumberFormatException.class, () -> {
  Integer.valueOf("abc");
});

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3️⃣ Using Integer.decode() (For the Fancy Number Nerds 🤓)

If you're dealing with different number formats like decimal, octal, or hexadecimal, Integer.decode() is here to save the day! 🦸‍♂️

• Decimal: Just use numbers, optionally prefixed with + or - (e.g., +100, -2022)
• Octal: Start with a 0 (e.g., 0404, +0100)
• Hexadecimal: Start with 0x or 0X (e.g., 0x334, +0x100)

public static Integer decode(String s) throws NumberFormatException

🎯 Example Conversions

Assertions.assertEquals(100, Integer.decode("+100"));
Assertions.assertEquals(64, Integer.decode("+0100"));
Assertions.assertEquals(256, Integer.decode("+0x100"));

Boom! Now you can handle numbers like a pro. 💪

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🎉 Conclusion

In this fun Java adventure, we: ✅ Learned to convert a String to int using parseInt() and valueOf(). ✅ Discovered decode() for handling decimal, octal, and hexadecimal formats. ✅ Realized Java doesn’t like nonsense inputs (hello, NumberFormatException! 👋).

Now, go forth and convert your strings like a Java champion! 🏆

Happy Coding! 🚀😃