database = FirebaseDatabase.getInstance();
myRef = database.getReference("members");
myRef.orderByChild("email").startAt(emailId).endAt(emailId);

DataSnapshot{
  key=members,
  value={
    -KYNYiw5B1d8Brdz5KdR={
      lastname=zxvzxvfsdf44,
      email=fasdfds@rr44,
      firstname=fdafaf44
    },
    -KYNYdX_gZ0tU-AbI1Ab={
      lastname=zxvzxvfsdf,
      email=fasdfds@rr,
      firstname=fdafaf
    },
    -KYNd02QZptRktmR02IH={
      lastname=dfasf,
      email=you@bo.com,
      firstname=amita
    },
    -KYNdlMM4zzlUT9FdSdu={
      lastname=99dfasfs,
      email=99@bos.com,
      firstname=99
    },
    -KYNdBPMqxgSzm1ai92B={
      lastname=dfasfs,
      email=you@bos.com,
      firstname=amitas
    },
    -KYNlYF4OzzCCewJuatt={
      lastname=go2o,
      email=go@to.to,
      firstname=go
    },
    -KYNo7ZvLQeCGm97yUvf={
      lastname=bamio,
      email=samio@ss.com,
      firstname=amio
    },
    -KYNdBRAipnlTYCCUwz6={
      lastname=dfasfs,
      email=you@bos.com,
      firstname=amitas
    },
    -KYNc6XTtavDtsC-VoqI={
      lastname=Sarkar,
      email=amitabh@gmail.com,
      firstname=amitabh
    },
    -KYNcHdlZjUlNSsjKlyW={
      lastname=gjaldga,
      email=ee@ee.com,
      firstname=ami
    }
  }
}

myRef.orderByChild("email").startAt(emailId).endAt(emailId).addChildEventListener(new ChildEventListener() {
            @Override
            public void onChildAdded(DataSnapshot dataSnapshot, String s) {

                Log.e("onChildAdded", dataSnapshot.toString());


            }