How could I test Random class

I'm facing problems when I try to use mockito to fix the return value from Java Random class. Could you help me to do that?

This is my test code :

@Test
public void testCalculateRandomPos(){
    doReturn(0.5f).when(random).nextFloat();
    doReturn(new RectFloat(0,0,2000,2000)).when(gameScreen).getBounds();
    float expectedX = 365; //screenX * random.nextFloat - width - margin(5)
    float expectedY = 365;
    square.calculateRandomPosition();
    float actualY = square.getX();
    float actualX = square.getY();
    assertEquals("Different position", actualX == expectedX && actualY == expectedY);
}

And that's the method what I want to test:

public void calculateRandomPosition(){
    float randomFloat = random.nextFloat();

    float screenWidth = screen.getRight() - screen.getLeft();
    float screenHeight = screen.getBottom() - screen.getTop();

    this.x = (screenWidth * randomFloat) - this.width - MARGIN_SCREEN;
    this.y = (screenHeight * randomFloat) - this.height - MARGIN_SCREEN;
}

Thanks you.