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我有一个名为 Main.java 的类。在此输出由 inputLine 显示，它是从 com 端口串行获取的字符串。我希望在同一个默认包中的其他一些类中使用这个字符串值。如何在其他类中调用此字符串？我做了一个静态并在方法之外声明它。现在我打电话给其他班级。当我尝试通过 Main.inputLine=1 在其他类中调用它时，它会说无与伦比的类型。

我还附上了错误的快照：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");
    }
}
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2 回答 2

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您正在尝试比较两件事，其中一件是对象（字符串）。使用equals(Object o).

（此外，原语之间的比较是使用==.

您正在尝试与整数值进行比较。您需要将整数值包装到一个字符串中，这样才有意义。

你要：

if(Main.inputLine.equals("1"))
{
    ...
}
于 2013-03-30T09:14:42.880 回答
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如果您尝试分配1给Main.inputLine然后使用以下：

Main.inputLine="1"

代替

Main.inputLine=1

如果您要比较字符串以检查 1，请使用以下命令：

Main.inputLine.equals("1");

代替

Main.inputLine == "1"
于 2013-03-30T09:35:46.850 回答