Java HashMap stores values in keys not intended

I am working on a program that tells you information about a package. However, I am having some issues with reverse dependencies (see under comment: Check for previous reverse dependencies and save them). The main issues is that when printing, right after putting the values in the HashMap, it seems to be storing them in the correct way. Nevertheless, printing the key and values of the map after finishing the process returns other values. Printed information can be seen after code.

public class MainActivity {
    public static void main (String[] args) {
        ArrayList<String> packages = new ArrayList<String>();
        ArrayList<String> descriptions = new ArrayList<String>();
        HashMap<String, ArrayList<String>> dependencies = new HashMap<>();
        HashMap<String, ArrayList<String>> revDependencies = new HashMap<>();
        int i = 0;
        String packageStart = "Package:";
        String descriptionStart = "Description:";
        String dependenciesStart = "Depends:";

        String packageName = "";

        BufferedReader reader;
        try {
            reader = new BufferedReader(new FileReader(
                    "/var/lib/dpkg/status"));
            String line = reader.readLine();
            while (line != null) {
                //System.out.println(line);

                if (line.startsWith(packageStart)) {
                    packageName = line.substring(packageStart.length()).trim();
                    packages.add(packageName);
                }
                if (line.startsWith(descriptionStart)) {
                    descriptions.add(line.substring(descriptionStart.length()).trim());
                }
                if (line.startsWith(dependenciesStart)) {
                    String subline = line.substring(dependenciesStart.length());
                    String[] dependenciesWithVersion = subline.split(", ");
                    ArrayList<String> dependenciesWOVersion = new ArrayList<String>();
                    ArrayList<String> currentRevDependencies = new ArrayList<String>();
                    String currentDependency;

                    for (String dependencyWithVersion : dependenciesWithVersion) {
                        int index = dependencyWithVersion.indexOf("(");
                        currentRevDependencies.clear();

                        //Take the version out of the package name
                        if (index != -1) {
                            currentDependency = dependencyWithVersion.substring(0, index);
                        } else {
                            currentDependency = dependencyWithVersion;
                        }
                        currentDependency.trim();
                        dependenciesWOVersion.add(currentDependency);

                        
                        //Check for previous reverse dependencies and save them
                        if (revDependencies.get(currentDependency) != null){
                            currentRevDependencies = revDependencies.get(currentDependency);
                        }

                        currentRevDependencies.add(packageName);
                        revDependencies.put(currentDependency, currentRevDependencies);

                        System.out.print("Package: " + packageName + " Dependency: " + currentDependency + " RevDepencencies: " + revDependencies.get(currentDependency) +  "\n");
                    }
                    dependencies.put(packageName, dependenciesWOVersion);

                    if (i == 2){
                        break;
                    }
                    i++;
                }
                line = reader.readLine();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }

        for (String key : revDependencies.keySet()){
            System.out.print(key + " " + revDependencies.get(key) + "\n");
        }

   }
} 

The following is printed on the screen:

Package: accountsservice Dependency:  dbus RevDepencencies: [accountsservice]
Package: accountsservice Dependency: libaccountsservice0  RevDepencencies: [accountsservice]
Package: accountsservice Dependency: libc6  RevDepencencies: [accountsservice]
Package: accountsservice Dependency: libglib2.0-0  RevDepencencies: [accountsservice]
Package: accountsservice Dependency: libpolkit-gobject-1-0  RevDepencencies: [accountsservice]
Package: acl Dependency:  libacl1  RevDepencencies: [acl]
Package: acl Dependency: libc6  RevDepencencies: [accountsservice, acl]
Package: acpi-support Dependency:  acpid  RevDepencencies: [acpi-support]

acpid  [acpi-support]
libaccountsservice0  [accountsservice, acl]
libpolkit-gobject-1-0  [accountsservice, acl]
libglib2.0-0  [accountsservice, acl]
libc6  [accountsservice, acl]
dbus [accountsservice, acl]
libacl1  []

The values that seem to be storing are not the ones printed when the process finishes.

The issue

Java passes passes object references by value. When you put the List currentRevDependencies into your revDependencies Map, what is being stored in the Map is not a copy of the List but merely an object reference. When currentRevDependencies is changed externally (like you calling clear on it), the list inside the map changes. That means for all keys added in one iteration of the while loop, the List reference will be the same, leading to the duplicate values you observe.

How to fix it

To fix this issue, create a new List for every key value pair you put into the Map instead of clearing the last Map each time like so:

//[...]
String subline = line.substring(dependenciesStart.length());
String[] dependenciesWithVersion = subline.split(", ");
ArrayList<String> dependenciesWOVersion = new ArrayList<String>();
String currentDependency;

for (String dependencyWithVersion : dependenciesWithVersion) {
    ArrayList<String> currentRevDependencies = new ArrayList<String>(); // <- instantiate new list each iteration

    //[...]

    revDependencies.put(currentDependency, currentRevDependencies);
}
dependencies.put(packageName, dependenciesWOVersion);
//[...]

Output:

Package: libasan0 Dependency:  gcc-4.8-base  RevDepencencies: [libasan0]
Package: libasan0 Dependency: libc6  RevDepencencies: [libasan0]
Package: libasan0 Dependency: libgcc1  RevDepencencies: [libasan0]
Package: libasan0 Dependency: libstdc++6  RevDepencencies: [libasan0]
Package: libvorbisfile3 Dependency:  libc6  RevDepencencies: [libvorbisfile3]
Package: libvorbisfile3 Dependency: libogg0  RevDepencencies: [libvorbisfile3]
Package: libvorbisfile3 Dependency: libvorbis0a  RevDepencencies: [libvorbisfile3]
Package: libquadmath0 Dependency:  gcc-4.9-base  RevDepencencies: [libquadmath0]
Package: libquadmath0 Dependency: libc6  RevDepencencies: [libasan0, libquadmath0]
 libc6  [libvorbisfile3]
libvorbis0a  [libvorbisfile3]
 gcc-4.9-base  [libquadmath0]
libgcc1  [libasan0]
libc6  [libasan0, libquadmath0]
libstdc++6  [libasan0]
 gcc-4.8-base  [libasan0]
libogg0  [libvorbisfile3]