值更改后，从地图上打印出条目

Question

I am working on a project in which I need to print out the data from the database in a certain way. Let's take an example, suppose in my database, I have below entries only-

Framework 1.0.0
BundleB 1.0.0
BundleC 1.0.0

Then my Java method that will make a call to the database which will return me a map of above data.

My map will have above data as below-

Key as Framework, Value as 1.0.0
Key as BundleB, Value as 1.0.0
Key as BundleC, Value as 1.0.0

Suppose, I started my program for the first time, then it will print out like this with the below code I have, which is perfectly fine.

Framework - 1.0.0

And then I am running background thread every 2 seconds that will make a call to the database and get all the data again from the database. And every two seconds, it will print out the same thing as below- (which is not what I want)

Framework - 1.0.0

I want to print out Framework - 1.0.0 for the first time when I am running my program but second time when the background thread is running, it should print out only when the version gets changed for that Framework, otherwise don't print out anything.

Meaning after some time, if somebody changes the version information in the database like this-

Framework 1.0.1
BundleB 1.0.0
BundleC 1.0.0

then only it should print out like this-

Framework - 1.0.1

I hope the questions is clear enough. Below is my code that I have so far.

public class Test {

    public static Map<String, String> bundleList = new LinkedHashMap<String, String>();

    private static Map<String, String> oldBundleList = new LinkedHashMap<String, String>();


    public static void main(String[] args) {

        getAttributesFromDatabase();

        loggingAfterEveryXMilliseconds();

    }


    private static void getAttributesFromDatabase() {

        Map<String, String> bundleInformation = new LinkedHashMap<String, String>();

        bundleInformation = getFromDatabase();
        if(!bundleInformation.isEmpty()) {
            oldBundleList = bundleList;
            bundleList = bundleInformation;
        }

        final Map<String, MapDifference.ValueDifference<String>> entriesDiffering = Maps.difference(oldBundleList, bundleList).entriesDiffering();
        if (!entriesDiffering.isEmpty()) {
            for (String key : entriesDiffering.keySet()) {
                bundleList.put(key, bundleList.get(key));
            } 
        }

        String version = bundleList.get("Framework");
        printOutZeroInformation("Framework", version);
    }

    private static void printOutZeroInformation(String string, String version) {
        System.out.println(string+" - "+version);       
    }

    private static Map<String, String> getFromDatabase() {

        Map<String, String> hello = new LinkedHashMap<String, String>();

        String version0 = "1.0.0";
        String version1 = "1.0.0";
        String version2 = "1.0.0";

        hello.put("Framework", version0);
        hello.put("BundleA", version1);
        hello.put("BundleB", version2);

        return hello;
    }

    private static void loggingAfterEveryXMilliseconds() {
        new Thread() {
            public void run() {
                while (true) {
                    try {
                        Thread.sleep(2000);
                    } catch (InterruptedException ex) {

                    }
                    getAttributesFromDatabase();
                }
            }
        }.start();
    }
}

Any help will be appreciated on this.

Answer 1

I didn't run it. I'm just giving you an idea. Try something same with the print as well. Let me know if you don't get it.

private static void getFromDatabase() {

        Map<String, String> hello = new LinkedHashMap<String, String>();            

        String version0 = "1.0.0";
        String version1 = "1.0.0";
        String version2 = "1.0.0";

        hello.put("Framework", version0);
        hello.put("BundleA", version1);
        hello.put("BundleB", version2);

        //The following code will update bundleList only when it's different from hello
        if (!bundleList.isEmpty()) {
            if (bundleList.get("Framework") != hello.get("Framework"))
                bundleList.put("Framework", version0)
            if (bundleList.get("BundleA") != hello.get("BundleA"))
                bundleList.put("BundleA", version1)
            if (bundleList.get("BundleB") != hello.get("BundleB"))
                bundleList.put("BundleB", version2)
        }
        else { //if this is the first time
            bundleList.put("Framework", version0)
            bundleList.put("BundleA", version1)
            bundleList.put("BundleB", version2)
        }
    }