private Button button;
    private Button button1;
    private Button button3;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        button = (Button)findViewById(R.id.button);
        button1 = (Button)findViewById(R.id.button3);
        button3 = (Button)findViewById(R.id.buttonx);
        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                openActivityx();
            }
        });
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               openActivity2();
            }
        });

        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                openActivity3();
            }
        });
    }

    public void openActivity2(){
        Intent intent2 = new Intent(this, Activity2.class);
        startActivity(intent2);
    }
    public void openActivity3(){
        Intent intent = new Intent(this, Model3.class);
        startActivity(intent);
    }
    public void openActivityx(){
        Intent intent = new Intent(this , modelx.class);
        startActivity(intent);
    }
}