Scanner 用法小结

brief introduction
Scanner is a class in java.util packager used for obtaining the input of the primitive types like int, double and String, etc. It is the easiest way to read input in a Java program, though not very efficient if you want an input method for secnarios where time is a constraint like in competitive programming.

• To create an object of Scanner class, we usually pass the predifined object System.in, which represents the standard input stream. We may pass an object of class file if we want to read input from a file.
• To read numerical values of a certain data type XYZ, the function to use is nextXYZ().
• To read Strings, we use nextLine().
• To read a single character, we use next().charAt(0). next() function returns the next token/word in the input as a string and charAt(0) function returns the first character in that String.

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