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Convert String to long in Java

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🏗️ Java Fun: Converting Strings to Longs 🎢​

Ever found yourself in a Java jungle trying to convert a String into a Long? Fear not, brave coder! Let's explore three ways to achieve this transformation while having a bit of fun. 🎉

⚡ Quick Reference​

String number = "2018"; // A String, not just a number!

long value1 = Long.parseLong(number, 10);  // The classic way!

long value2 = Long.valueOf(number);  // Another solid choice!

long value3 = new Long(number);  // Deprecated, but hey, it’s an option!

🛠️ 1. Using Long.valueOf(String)​

Think of Long.valueOf() as a magic decoder ring for numbers in String disguise. It takes a String, checks if it's made of decimal digits, and poof!—out comes a long. The first character can be a + or -, but no funny business, or it throws a tantrum (NumberFormatException). 🤯

🎭 Example​

String positiveNumber = "+12001";
long value1 = Long.valueOf(positiveNumber);   // 12001L

String negativeNumber = "-22002";
long value2 = Long.valueOf(negativeNumber);   // -22002L

🚨 Warning! Try sneaking in a non-number character, and Java will catch you red-handed:

Assertions.assertThrows(NumberFormatException.class, () -> {
  Long.valueOf("alexa");
});

🎯 2. Using Long.parseLong(String)​

This method is valueOf()'s twin, just without the extra wrapping. Same rules apply—only decimal digits and an optional + or - sign are allowed. It does the job, and it does it well! 🏆

🏋️‍♂️ Example​

String positiveNumber = "+12001";
long value1 = Long.parseLong(positiveNumber);   // 12001L

String negativeNumber = "-22002";
long value2 = Long.parseLong(negativeNumber);   // -22002L

🕵️‍♂️ Bonus Trick: Different Number Bases​

Want to parse a hexadecimal (base 16) number? No problem!

String numberInHex = "-FF";
long value = Long.parseLong(numberInHex, 16);   // -255L

🚀 3. Using new Long(String) Constructor (Old School)​

Back in the day (before Java 9), you could create a Long object using the new Long(String) constructor. But like disco pants, this approach is deprecated. 🕺

long value = new Long("100");   // 100L

Use parseLong() instead—it’s faster, cooler, and Java won’t yell at you. 😎

☠️ 4. Beware the NumberFormatException Monster! 🐉​

If your input string contains anything other than decimal digits (and an optional sign at the start), Java will throw a NumberFormatException at you faster than you can say "Oops!" 😱

String number = "12001xyz";
long value = Long.parseLong(number);

💥 Boom! Runtime error incoming:

Exception in thread "main" java.lang.NumberFormatException: For input string: "12001xyz"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Long.parseLong(Long.java:589)
    at java.lang.Long.<init>(Long.java:965)
    at com.howtodoinjava.StringExample.main(StringExample.java:9)

So, keep those Strings clean, stick to digits, and happy coding! 🚀

🎉 Happy Learning!! 🧑‍💻​