Converting from Integer to BigInteger

Grasping the conversion

Transitioning between Integer and BigInteger is a vital skill when handling massive numbers that exceed the standard limits of primitive data types. This is the domain of BigInteger, a power player capable of managing infinitely gargantuan numbers.

Conversion methodologies

Turning BigInteger back into Integer

Need to go back? Here's how:

Integer intVal = bigIntVal.intValueExact(); // Time travel back to Integer. Mind your head!
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Remember, intValueExact() throws an ArithmeticException if the BigInteger is too massive or too minuscule so ensure to catch this exception to avoid unnecessary meltdowns.

String-based conversion

We can also play with strings:

BigInteger bigIntFromString = new BigInteger("123456"); // Trust me, this is a string!
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What about converting BigInteger back to a string? Piece of cake!

String strFromBigInt = bigIntVal.toString();
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This can come in handy for certain scenarios, like serialization or text-based operations.

Utilizing larger primitive types

Need something a bit bigger?

long longFromBigInt = bigIntVal.longValueExact(); 
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longValueExact(), much like its cousin intValueExact(), will summon an exception for values that don't fit the long type's size limitations.

Common pitfalls

No direct casting

Java does not permit direct type casting from an Integer object to a BigInteger.

BigInteger bigInteger = (BigInteger) integerObject; // Error! No cookies for you!
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Trying this will undoubtedly result in a compilation error.

Inefficient string concatenation

This approach may seem clever, but is about as much use as a chocolate teapot:

BigInteger bigIntIncorrect = new BigInteger(integerVar + ""); // Don't do this at home!
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Though it technically works, it's both egregious to performance efficiency and abominable for type safety.

Common problems and solutions

While shifting between varying numeric types, watch for sneaky overflow or truncation errors. Use functions like intValueExact() to detect these issues before they wreak havoc.

Null values

Never forget to check for null prior to conversion. Otherwise, a NullPointerException might crash your party:

if (integerVar != null) {
    BigInteger bigIntVal = BigInteger.valueOf(integerVar.intValue());
}
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Performance-minded practices

In apps where speed is everything, always aim to minimize boxing and unboxing to avoid creating surplus objects:

BigInteger bigIntVal = BigInteger.valueOf(intVal); // Efficient conversion
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This tip could be the difference between coming first or last in the app race.

BigInteger optimization

Conserving resources

In contexts where BigInteger instances are frequently spawned from integers, a cache of frequently used values might save a lot of resources.

Arithmetic operations with BigInteger

BigInteger sports an array of methods for arithmetic operations that parallel primitive types while adding the advantage of endless magnitude.

BigInteger sum = bigInt1.add(bigInt2);  // It adds up, doesn't it?
BigInteger result = bigInt1.multiply(bigInt2); // What a product-ive BigNumber!
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