public static void getData() {
    Map<String, String> ronaldo = initRonaldo();
    Map<String, String> messi = initMessi();

    ronaldo.replaceAll(messi::put);

    System.out.println("Ronaldo: " + ronaldo);
    System.out.println("Messi: " + messi);
}

public static Map<String, String> initRonaldo() {
    Map<String, String> ronaldo = new HashMap<>();
    ronaldo.put("team", "Real Madrid");
    ronaldo.put("number", "7");
    return ronaldo;
}

public static Map<String, String> initMessi() {
    Map<String, String> messi = new HashMap<>();
    messi.put("team", "FC Barcelona");
    messi.put("number", "10");
    return messi;
}