Java Language Console I/O Implementing Basic Command-Line Behavior
Example
For basic prototypes or basic command-line behavior, the following loop comes in handy.
public class ExampleCli {
private static final String CLI_LINE = "example-cli>"; //console like string
private static final String CMD_QUIT = "quit"; //string for exiting the program
private static final String CMD_HELLO = "hello"; //string for printing "Hello World!" on the screen
private static final String CMD_ANSWER = "answer"; //string for printing 42 on the screen
public static void main(String[] args) {
ExampleCli claimCli = new ExampleCli(); // creates an object of this class
try {
claimCli.start(); //calls the start function to do the work like console
}
catch (IOException e) {
e.printStackTrace(); //prints the exception log if it is failed to do get the user input or something like that
}
}
private void start() throws IOException {
String cmd = "";
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
while (!cmd.equals(CMD_QUIT)) { // terminates console if user input is "quit"
System.out.print(CLI_LINE); //prints the console-like string
cmd = reader.readLine(); //takes input from user. user input should be started with "hello", "answer" or "quit"
String[] cmdArr = cmd.split(" ");
if (cmdArr[0].equals(CMD_HELLO)) { //executes when user input starts with "hello"
hello(cmdArr);
}
else if (cmdArr[0].equals(CMD_ANSWER)) { //executes when user input starts with "answer"
answer(cmdArr);
}
}
}
// prints "Hello World!" on the screen if user input starts with "hello"
private void hello(String[] cmdArr) {
System.out.println("Hello World!");
}
// prints "42" on the screen if user input starts with "answer"
private void answer(String[] cmdArr) {
System.out.println("42");
}
}
