Insert into firebase real-time database with getuid instead of getkey

I am inserting data into the firebase real-time database and then getting the data and displaying it on a graph but when i insert into the database now i am using the unique getkey() method to insert the values but i would like to use the getuid() method as the user is already authenticated in the app. I'd like to know how I can change the getkey() to use the getuid().

This is my current code: The getkey() method is in the setListneners() method

FirebaseDatabase database;
DatabaseReference reference;
SimpleDateFormat simpleDateFormat = new SimpleDateFormat("dd/mm/yyyy");
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_weight); 
Btn_Display = findViewById(R.id.btn_display);
graphView = findViewById(R.id.weight_graph);
series =  new LineGraphSeries();
graphView.addSeries(series);
database = FirebaseDatabase.getInstance();
reference = database.getReference("WeightGraph");
setListeners();
}
private void setListeners() {
Btn_Display.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View view) {
String id = reference.push().getKey();
long x = new Date().getTime();
int y = Integer.parseInt(weight.getText().toString());
PointValue pointValue =  new PointValue(x, y);
reference.child(id).setValue(pointValue);
}
});
graphView.getGridLabelRenderer().setNumHorizontalLabels(2);
graphView.getGridLabelRenderer().setNumVerticalLabels(2);
graphView.getGridLabelRenderer().setLabelFormatter(new DefaultLabelFormatter(){
@Override
public String formatLabel(double value, boolean isValueX) {
if(isValueX){
return simpleDateFormat.format(new Date((long) value));
}else{
return super.formatLabel(value, isValueX);
}
}
});
}
@Override
protected void onStart() {
super.onStart();
reference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
DataPoint[] dataPoints = new DataPoint[(int) snapshot.getChildrenCount()];
int index = 0;
for(DataSnapshot dataSnapshot : snapshot.getChildren()){
PointValue pointValue = dataSnapshot.getValue(PointValue.class);
dataPoints[index] = new DataPoint(pointValue.getxValue(), pointValue.getyValue());
series.resetData(dataPoints);
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}

@Override
protected void onStart() {
super.onStart();
FirebaseUser mAuth = FirebaseAuth.getInstance().getCurrentUser()
reference.addValueEventListener(new ValueEventListener() {
@Override
public void onDataChange(@NonNull DataSnapshot snapshot) {
DataPoint[] dataPoints = new DataPoint[(int) snapshot.getChildrenCount()];
int index = 0;
for(DataSnapshot dataSnapshot : snapshot.getChildren()){
PointValue pointValue = dataSnapshot.getValue(PointValue.class);
dataPoints[index] = new DataPoint(pointValue.getxValue(), pointValue.getyValue());
series.resetData(dataPoints);
}
}
@Override
public void onCancelled(@NonNull DatabaseError error) {
}
});
}

Then you can get Uid

mAuth.getUid()

If you want to write the data under the user's UID instead of the key generated by push(), you'd do something like this:

String id = FirebaseAuth.getInstance().getCurrentUser().getUid();
long x = new Date().getTime();
int y = Integer.parseInt(weight.getText().toString());
PointValue pointValue =  new PointValue(x, y);
reference.child(id).setValue(pointValue);

If you want to store a list of points for each user, you'd change that last line to:

reference.child(id).push().setValue(pointValue);

So this way you get a list of auto-generated (push) IDs under each UID.