Why Does Java's BigInteger Class Have BigInteger(String) but Not BigInteger(long)?

Why does Java's BigInteger class have a constructor that accepts a String but not one that accepts long values?

In Java, the BigInteger class is designed to handle arbitrary-precision integers, making it essential for working with large values that exceed the limits of primitive data types like long. The existence of a constructor for String but not for long is rooted in performance considerations and the nature of arbitrary-precision computations.

// Creating a BigInteger from a long value
long longValue = 9876543210L;
BigInteger bigIntFromLong = BigInteger.valueOf(longValue); // Recommended method

// Alternatively, using String
BigInteger bigIntFromString = new BigInteger(Long.toString(longValue)); // Less efficient but valid

Causes

• The BigInteger class is intended for handling integers larger than those representable by primitive data types such as long, which has a fixed size (64 bits).
• The value of long can lead to overflow when it surpasses its maximum limit (9,223,372,036,854,775,807). By using a String representation, developers can create BigInteger instances for values that are much larger than this limit.
• Designing the constructor to take a String allows for a more flexible and robust way to construct BigIntegers without the risk of overflow.

Solutions

• To create a BigInteger from a long value, simply pass the long value to the BigInteger constructor that accepts a String, like this:
• ```java BigInteger bigIntegerFromString = new BigInteger(Long.toString(longValue)); ```
• Alternatively, use the static method BigInteger.valueOf(long val) which internally converts the long to a BigInteger efficiently. This is the recommended approach for creating BigInteger instances from long values.

Mistake: Attempting to create a BigInteger directly from a long using an unsupported constructor.

Solution: Use BigInteger.valueOf(long val) instead.

Mistake: Not considering the potential for overflow when using primitive types.

Solution: Always prefer using BigInteger with larger values, especially when dealing with large integer computations.