Algorithm used to draw a translucent image onto another

Question

What is the algorithm Java used to draw a translucent image onto another?

Let say I have a pixel value of the base image as 0xc8ff708f, and the pixel to be drawn directly on top of it is 0xba46ff3f, how does Java determine what value the resulting pixel have when drawn through the following code:

baseImage.getGraphics().drawImage(secondImage, 0, 0,
    baseImage.getWidth(), baseImage.getHeight());

When both images are exactly the same size.