Input / Output in Java

Using hsa Console Class

I/O in Java

Java doesn't have commands to input primitive data types (no scanf, cin)

Similarly, output facilities are limited\

Therefore we use the Console class for these facilities, as well as some graphics.

Simple I/O

We convert the Java input stream to a data input stream.

DataInputStream stdin = new DataInputStream(System.in);

Once this is done we can use the readLine method.

For output we can use either

System.out.println (with line feed) or

System.out.print

Sample Program

Reading Integers

Need to have console set up, see examples

int age;

c.print("Please enter your age: ");

age = c.readInt();

c.print("Your age next year will be");

c.println(age + 1);

Output last letter program

String Word;

final String SENTINEL = "stop";

c.println("Enter words");

word = c.readLine();

while (!word.equals(SENTINEL)) {

c.println(word.charAt(word.length()-1));

word = c.readLine(); }

Reading from a file

Need to open input stream.

BufferedReader input;

input = new BufferedReader(new FileReader(filename));

To get data

word = input.readline()

To get number

number = Integer.parseInt(word);

Output to a file

Use class PrintWriter

PrintWriter output;

String filename;

c.println("What is filename:");

filename = c.readLine();

output= new PrintWriter(new FileWriter(filename));

for (int i=0; i<10; i++)

output.println(i);

output.close();