The scanner class introduced with J2SE 5.0 is a beneficial new class that can parse text for primitive types and substrings using regular expre4ssions. The scanner java can obtain the text from sources such as a string object, an input stream, a file, and any class that implements the readable interface. the scanner splits into substrings, or tokens, separated by delimiters, which by default consists of any white space. The tokens can then be obtained as strings or as primitive types if that is what they represent.
Scanner scanner= new Scanner(System.in)
This is the code snippet that shows us how to read an integer through scanner class. For each of the primitive types, there is a corresponding nextxxx() method that returns a value of that type. If the string cannot be interpreted as that type, then an input mismatch exception is thrown. A scanner object will divide a line of input into tokens or fields using white space to delimit the tokens.
If the input has been exhausted or if the token cannot be converted to the desired type, then the above methods will throw exceptions. To avoid having exceptions thrown, we can check whether or not a token exists and whether or not it conforms to the desired type using a few sets of methods that are required.
DISCARDING A SCANNER:
When we have finished using a scanner such as when we have exhausted a line of input or have reached the end of life, we should close the scanner using the close method. If we do not close it using the close method then the java will not garbage collect the scanner object, and we will have a memory leak in our program.
SCANNER FOR INPUT FROM A FILE:
Well to use the scanner class we have to obtain the input from the console. The Scanner class can read from a file just as easily as it can from the console. To understand this, let us take an example.
The program uses a scanner to scan past the text at the beginning of the file and then reads each of the primitive type values. There are many options with the pattern matching capabilities of the scanner to jump past the initial text. We choose a simple technique of looking for the 1st primitive type value, which is a Boolean type value. So we loop over calls to has next boolean() until we find a Boolean value. This method and the similar ones for other primitive types, look ahead at the next token and return true or false depending on whether the token is of the type indicated. It does not jump past the token. So, if the next token is not a Boolean, we use the next () method to skip this token and examine the next one. When we find the Boolean, we break out of the loop.
There are 2 types of printing models in java, and they are:
PRINTABLE JOBS and
The 1st one is the simpler of the 2 printing models. This uses a one-page printer for the entire document. Pages are rendered in sequence starting from 0. While on the other hand, the next one offers more flexibility than the pintables and each page in the pintables can feature a different layout. They are most commonly used with the books where we can find a collection of pages that can have different formats.
What is a scanner object in Java?
A scanner object in java used to scan something from the input stream or input buffer of your machine. We usually use a scanner object for taking input from the user. For example, consider the subsequent code- Scanner sc = new Scanner(); int a = sc.nextInt(); In this code, so maybe a scanner type object. you’ll visualize like that sc object scan an integer number from input buffer or input stream ( because I write sc.nextInt() ) and set that integer value inside the variable a. It’s something lake take one thing from the input stream and put that thing in another location.
Apart from providing various classes for obtaining in out, java also provides classes for printing on the printer through java 2D printing API. We have already learned about the java feature and the OOP regarding the java and now the scanner class that we have learned about also provides us an ample amount of information regarding the java class. Though buffered reader can also be used instead of scanner yet the syntax of scanner seems to easier placed than the buffered reader.
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