Test java programs that read from stdin and write to stdout
I am writing some code for a programming contest in java. The input to the program is given using stdin and output is on stdout. How are you folks testing programs that work on stdin/stdout? This is what I am thinking:
Since System.in is of type InputStream and System.out is of type PrintStream, I wrote my code in a func with this prototype:
void printAverage(InputStream in, PrintStream out)
Now, I would like to test this using junit. I would like to fake the System.in using a String and receive the output in a String.
@Test
void testPrintAverage() {
String input="10 20 30";
String expectedOutput="20";
InputStream in = getInputStreamFromString(input);
PrintStream out = getPrintStreamForString();
printAverage(in, out);
assertEquals(expectedOutput, out.toString());
}
What is the 'correct' way to implement getInputStreamFromString() and getPrintStreamForString()?
Am I making this more complicated than it needs to be?
Try the following:
String string = "aaa";
InputStream stringStream = new java.io.ByteArrayInputStream(string.getBytes())
stringStream is a stream that will read chard from the input string.
OutputStream outputStream = new java.io.ByteArrayOutputStream();
PrintStream printStream = new PrintStream(outputStream);
// .. writes to printWriter and flush() at the end.
String result = outputStream.toString()
printStream is a PrintStream that will write to the outputStream which in turn will be able to return a string.
EDITED: Sorry I misread your question.
Read with scanner or bufferedreader, The latter is much faster than the former.
Scanner jin = new Scanner(System.in);
BufferedReader reader = new BufferedReader(System.in);
Write to stdout with print writer. You can also print directly to Syso but this is slower.
System.out.println("Sample");
System.out.printf("%.2f",5.123);
PrintWriter out = new PrintWriter(System.out);
out.print("Sample");
out.close();