IntegerparseInt

IntegerparseInt is a common term for a function that converts a string representation of an integer into an actual numeric value. In Java, the standard implementation is the static method Integer.parseInt in the java.lang.Integer class. A variant, parseInt(String s, int radix), accepts an explicit numeral base (radix).

In Java, the method interprets the characters in the input string according to the specified radix, with an optional leading sign (+ or -). The radix must be between 2 and 36. The return type is int. If the input string is null, a NullPointerException is thrown. If the string contains digits not valid for the given radix, or if the numeric value does not fit in an int, a NumberFormatException is thrown.

Examples: Integer.parseInt("123") returns 123. Integer.parseInt("-42") returns -42. Integer.parseInt("FF", 16) returns 255. The method does not accept decimal points or other non-digit characters outside a sign and the digits for the chosen radix.

Notes and related points: The parseInt method is designed for primitive int results; Integer.valueOf can also be used but returns an Integer object (with possible boxing). Whitespace generally makes the input invalid for parseInt, and overflow is reported via an exception rather than truncation. The concept of parseInt appears in other languages as well, often with slightly different rules and error behavior (for example, JavaScript’s parseInt and its handling of radix and NaN).