如何调用一个字符串出现在同一个包的另一个类中

Question

I have this class called Main.java. In this the output is shown by inputLine which is a string taken serially from the com port. I want this string value to be used in some other class which is in the same default package. How do I call this string in other class? I have made a static and declared it outside the method. Now do I call in other class. When I try calling it in other class by Main.inputLine=1 then it says incomparable types.

Also I'm attaching a snapshot of the error: http://oi45.tinypic.com/2gvo5u9.jpg

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.OutputStream;
import gnu.io.CommPortIdentifier;
import gnu.io.SerialPort;
import gnu.io.SerialPortEvent;
import gnu.io.SerialPortEventListener;
import java.lang.String;
import java.util.Enumeration;


public class Main implements SerialPortEventListener
{
    SerialPort serialPort;
        /** The port we're normally going to use. */
    private static final String PORT_NAMES[] = {
            "COM30", // Windows
    };
    /**
    * A BufferedReader which will be fed by a InputStreamReader
    * converting the bytes into characters
    * making the displayed results code page independent
    */
    public BufferedReader input;
    /** The output stream to the port */
    public OutputStream output;
    /** Milliseconds to block while waiting for port open */
    private static final int TIME_OUT = 2000;
    /** Default bits per second for COM port. */
    private static final int DATA_RATE = 9600;

    public void initialize() {
        CommPortIdentifier portId = null;
        Enumeration portEnum = CommPortIdentifier.getPortIdentifiers();

        //First, Find an instance of serial port as set in PORT_NAMES.
        while (portEnum.hasMoreElements()) {
            CommPortIdentifier currPortId = (CommPortIdentifier) portEnum.nextElement();
            for (String portName : PORT_NAMES) {
                if (currPortId.getName().equals(portName)) {
                    portId = currPortId;
                    break;
                }
            }
        }
        if (portId == null) {
            System.out.println("Could not find COM port.");
            return;
        }

        try {
            // open serial port, and use class name for the appName.
            serialPort = (SerialPort) portId.open(this.getClass().getName(),
                    TIME_OUT);

            // set port parameters
            serialPort.setSerialPortParams(DATA_RATE,
                    SerialPort.DATABITS_8,
                    SerialPort.STOPBITS_1,
                    SerialPort.PARITY_NONE);

            // open the streams
            input = new BufferedReader(new InputStreamReader(serialPort.getInputStream()));
            output = serialPort.getOutputStream();

            // add event listeners
            serialPort.addEventListener(this);
            serialPort.notifyOnDataAvailable(true);
        } catch (Exception e) {
            System.err.println(e.toString());
        }
    }

    /**
     * This should be called when you stop using the port.
     * This will prevent port locking on platforms like Linux.
     */
    public synchronized void close() {
        if (serialPort != null) {
            serialPort.removeEventListener();
            serialPort.close();
        }
    }

    /**
     * Handle an event on the serial port. Read the data and print it.
     */
        public static String inputLine;
    public synchronized void serialEvent(SerialPortEvent oEvent) {
        if (oEvent.getEventType() == SerialPortEvent.DATA_AVAILABLE) {
            try {
                inputLine=input.readLine();
                                System.out.println(inputLine);

            } catch (Exception e) {
                System.err.println(e.toString());
            }
        }
        // Ignore all the other eventTypes, but you should consider the other ones.
    }

    public static void main(String[] args) throws Exception {
        Main main = new Main();
        main.initialize();
        Thread t=new Thread() {
            public void run() {
                //the following line will keep this app alive for 1000 seconds,
                //waiting for events to occur and responding to them (printing incoming messages to console).
                try {Thread.sleep(1000000);} catch (InterruptedException ie) {}
            }
        };
        t.start();
        System.out.println("Started");
    }
}

Answer 1

You're trying to compare two things and one of them is an Object (String). Use equals(Object o) .

(Besides, comparison between primitives is done using == .

You're trying to compare to an integer value. You need to wrap the integer value to a String for this to make much sense.

You want:

if(Main.inputLine.equals("1"))
{
    ...
}

Answer 2

If you are trying to assign 1 to Main.inputLine then use the following :

Main.inputLine="1" 

instead of

Main.inputLine=1

And if you are comparing the String to check for 1 then use the following:

Main.inputLine.equals("1");

instead of

Main.inputLine == "1"