Using BigInteger Multiply operator

问题:

I was wondering if there was a way to multiply BigInteger variables together, because the * operator cannot be applied to BigInteger.

So I was wondering if it was possible to multiply two BigIntegers together without using the * operator.

回答1:

You use BigIntegers multiply() method like so:

BigInteger int1 = new BigInteger("131224324234234234234313");
BigInteger int2 = new BigInteger("13345663456346435648234313");
BigInteger result =  int1.multiply(int2) 

I should have pointed out a while ago that BigInteger is immutable. So any result of an operation has to be stored into a variable. The operator or operand are never changed.

回答2:

Easier way to implement:

int i = 5;
BigInteger bigInt = new BigInteger("12345678901");
BigInteger result = bigInt.multiply(BigInteger.valueOf(i))

回答3:

You can use the multiply(BigInteger) method in BigInteger. So:

BigInteger result = someBigInt.multiply(anotherBigInt);

BigInteger in Java API

回答4:

The result multiplying these specific factors

A: 131224324234234234234313

B: 13345663456346435648234313

Could be this one (I hope I am correct):

R: 1751275668516575787795211751170772134115968581969

Both are considered being two positive integers. And the technique used was Karatsuba’s method

int ab = (mul1) * 10^n + (mul3 - mul1 - mul2) * 10^n/2 + mul2;