Java BigInteger.shiftLeft() is a method in the Java BigInteger class that returns a new BigInteger obtained by shifting the bits of the current BigInteger to the left by a specified number of positions. This is equivalent to multiplying by a power of two. Introduced in Java 2004 with Java 5, shiftLeft() is commonly used in cryptography and bit manipulation tasks.

https://docs.oracle.com/javase/8/docs/api/java/math/BigInteger.html