Link error (symbol from plugin)* - c++

Question

Its been a while since ive coded in c++/c and im a little confused as to what im doing wrong
I have three files, 2 .h and one .cpp.
The files are as follow
Base Menu
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#define OLED_RESET 4
#define SSD1306_LCDHEIGHT 64
Adafruit_SSD1306 display(OLED_RESET);
class BaseMenu {
public:
// for moving the menu up and down
void moveDownMenu();
void moveUpMenu();
void selectMenu();
// for changing the text and the positions
void incrementText();
void decrementText();
protected:
//
char menuTitlePos1[20];
char menuTitlePos2[20];
char menuTitlePos3[20];
bool is_menuPos1_selected = true;
bool is_menuPos2_selected = false;
bool is_menuPos3_selected = false;
private:
virtual void AbstractClass() = 0;
};
MainMenu.h
#include "BaseMenu.h"
#include <string.h>
#define ARRAYSIZE 4
class MainMenu : BaseMenu {
private:
// Constructor
MainMenu() {};
public:
static void init();
};
MainMenu.cpp
#include "MainMenu.h"
void MainMenu::init() {
// clearing display
display.clearDisplay();
display.display();
display.setTextSize(1);
display.setTextColor(WHITE);
for (int i = 0; i < ARRAYSIZE; i++) {
if (i == 1) {
display.setTextSize(1);
display.setTextColor(BLACK, WHITE);
//display.println(MainMenuTitles[i]);
}
else {
display.setTextSize(1);
display.setTextColor(WHITE);
//display.println(MainMenuTitles[i]);
}
}
display.display();
}
When ever i go to build the code i get the following error.
MainMenu.cpp.o (symbol from plugin)*: In function display
(.text+0x0)*: multiple definition of display
TestingLibrary.cpp.o (symbol from plugin)*: (.text+0x0): first defined here
collect2.exe*: error: ld returned 1 exit status
Can someone please shed some light as to what i'm doing wrong?