public void left(){
        boolean isChanged = false;
        for (int i = 0; i < FIELD_WIDTH; i++) {
            if ( mergeTiles(gameTiles[i]) | compressTiles(gameTiles[i])) {
                isChanged = true;
            }
        }
        if (isChanged) {
            addTile();
        }
    }
и
public void left(){
       boolean isEdit = false;
       for (int i = 0; i <FIELD_WIDTH ; i++) {
           boolean isEditComp = compressTiles(gameTiles[i]);
           boolean isEditMarge = mergeTiles(gameTiles[i]);
           if(isEditComp | isEditMarge){
               isEdit = true;
           }
       }
       if(isEdit){
           addTile();
       }
   }