transformer un string en Biginteger java

In Java, you can use the BigInteger class to represent a large integer value that can be any size, including values that are too large to be stored in the long primitive type.

To convert a string representation of a large integer value into a BigInteger object, you can use the BigInteger.valueOf() method or the BigInteger constructor that takes a string as an argument.

Here's an example of how you can use the BigInteger.valueOf() method to convert a string to a BigInteger object:

String str = "12345678901234567890";
BigInteger bi = BigInteger.valueOf(Long.parseLong(str));

In this example, the str variable is a string that represents a large integer value. The Long.parseLong() method is used to parse the string as a long value, and the resulting long value is passed as an argument to the BigInteger.valueOf() method. The BigInteger.valueOf() method returns a BigInteger object that represents the same value as the long value.

Alternatively, you can use the BigInteger constructor that takes a string as an argument to convert a string to a BigInteger object. Here's an example of how you can use the BigInteger constructor to convert a string to a BigInteger object:

String str = "12345678901234567890";
BigInteger bi = new BigInteger(str);

In this example, the str variable is a string that represents a large integer value. The BigInteger constructor is called with the str variable as an argument, and the resulting BigInteger object is stored in the bi variable.