Unable to save readLine(); to the string variable

Question

I'm trying to save readLine() output to the variable (it contains only one single line) to compare this lines in the future. But variables do not change their values:

try {
                        String VersName = "src/bin/version.txt";
                        BufferedReader br = null;
                        br = new BufferedReader(new FileReader(VersName));
                        URL url = new URL("ftp://31.130.206.175/current_versions/vers");

                        // read text returned by server
                        BufferedReader in = new BufferedReader(new InputStreamReader(url.openStream()));
                        System.out.println(br.readLine());
                        System.out.println(in.readLine());

                        String aa = null;
                        String bb = null;
                        aa = br.readLine();
                        bb = in.readLine();
                        System.out.println("***" + aa + "***" + bb + "***");

                        in.close();
                        br.close();

                    } catch (MalformedURLException e3) {
                        System.out.println("Malformed URL");
                    } catch (IOException e4) {
                        System.out.println("I/O Error");
                    }

Output:

0.0.0
0.1.0
***null***null***

When I'm trying to covert them to Strings (aa = br.readLine().toString();), I have an exception:

0.0.0
0.1.0
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
    at Launcher.SimpleSwingBrowser$3.actionPerformed(SimpleSwingBrowser.java:209)
    at javax.swing.AbstractButton.fireActionPerformed(AbstractButton.java:2022)
    at javax.swing.AbstractButton$Handler.actionPerformed(AbstractButton.java:2348)
    at javax.swing.DefaultButtonModel.fireActionPerformed(DefaultButtonModel.java:402)
    at javax.swing.DefaultButtonModel.setPressed(DefaultButtonModel.java:259)
    at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(BasicButtonListener.java:252)
    at java.awt.Component.processMouseEvent(Component.java:6535)
    at javax.swing.JComponent.processMouseEvent(JComponent.java:3324)
    at java.awt.Component.processEvent(Component.java:6300)
    at java.awt.Container.processEvent(Container.java:2236)
    at java.awt.Component.dispatchEventImpl(Component.java:4891)
    at java.awt.Container.dispatchEventImpl(Container.java:2294)
    at java.awt.Component.dispatchEvent(Component.java:4713)
    at java.awt.LightweightDispatcher.retargetMouseEvent(Container.java:4888)
    at java.awt.LightweightDispatcher.processMouseEvent(Container.java:4525)
    at java.awt.LightweightDispatcher.dispatchEvent(Container.java:4466)
    at java.awt.Container.dispatchEventImpl(Container.java:2280)
    at java.awt.Window.dispatchEventImpl(Window.java:2750)
    at java.awt.Component.dispatchEvent(Component.java:4713)
    at java.awt.EventQueue.dispatchEventImpl(EventQueue.java:758)
    at java.awt.EventQueue.access$500(EventQueue.java:97)
    at java.awt.EventQueue$3.run(EventQueue.java:709)
    at java.awt.EventQueue$3.run(EventQueue.java:703)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
    at java.awt.EventQueue$4.run(EventQueue.java:731)
    at java.awt.EventQueue$4.run(EventQueue.java:729)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:76)
    at java.awt.EventQueue.dispatchEvent(EventQueue.java:728)
    at java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:201)
    at java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:116)
    at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:105)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:101)
    at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:93)
    at java.awt.EventDispatchThread.run(EventDispatchThread.java:82)

Is there any way to save them to variable?

Thank you.

If the data only contains one line why are you calling `readLine()` four times? But the output you have provided shows clearly *two* lines: your explanation? And what is `in`, and what is the basis for your belief that it isn't null? — user207421, Nov 02 '16 at 10:36

score 0 · Accepted Answer · edited Nov 02 '16 at 10:49

Your problem is here

System.out.println(br.readLine());
System.out.println(in.readLine());

You read your line, so it is no longer available for your

aa = br.readLine();
bb = in.readLine();

And so you read nothing.

Try to reorder your instructionslike this (for example):

String aa = br.readLine();
String bb = in.readLine();

System.out.println(aa);
System.out.println(bb);

It should be better ;)

Unable to save readLine(); to the string variable

1 Answers1