Java Float Input
Java programs can read external data from input sources such as files. Using classes of the Java input and output libraries, developers can code applications to read numerical input such as floating point numbers. Depending on the data in an input resource, developers may need to implement control structures such as loops in their programs, to read from a source continually until no numerical data is left to process.
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Input Classes
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Java developers can choose from a range of classes to facilitate their input processes. The Scanner class provides methods for reading float inputs. An application can therefore create an instance of the Scanner class, then call its methods to read floating point numbers from a specified location. To use the Scanner class, programs need to import the package "java.io" and instantiate objects of other types, such as BufferedReader and FileReader, specifying the name and location of the input resource, before passing these to the Scanner constructor method. Once a program has an object of Scanner type, it can call various input methods for reading strings and specific number types, including floats.
Methods
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The Scanner class provides a variety of input methods for reading data. The "nextFloat" method reads the next token in a file as a floating point number. The following sample code demonstrates the technique:
float aNumber = scanner.nextFloat();This code will only work if the file still has content that the program has not yet read and if the next token can be processed as a floating point number. If the input is not a float number type, the program may throw an exception and crash.
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Control Structures
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Java input operations normally involve control structures such as loops. By using a "while" loop, programmers can be sure that their input operations will not attempt to read from an empty file. The following sample code demonstrates a common structure in such programs:
while(scanner.hasNextFloat()) {
float aNumber = scanner.nextFloat();
}The "while" loop will only execute if the file still has a float token to read. Inside the loop, the programmer can implement any necessary processing on the float item that has just been read in.
Considerations
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In Java, any input operation presents a risk of error. If a file cannot be found or the input data is not of the type expected, an exception may arise. For this reason, programmers normally include their float reading operations inside "try" blocks, with "catch" blocks defining what will happen if an exception is thrown. The following sample code outline demonstrates this structure:
try {
//attempt float input
}
catch(IOException floatException) {
//implement exception handling
}If a programmer attempts to carry out input operations in an Integrated Development Environment without using "try" and "catch" blocks, the IDE will display error messages and prevent the code from compiling.
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References
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