Meaning of *= in Java

Question

I see an unfamiliar notation in the Android source code: *=

For example: density *= invertedRatio;

I am not familiar with the star-

Answer 1

In Java, the *= is called a multiplication compound assignment operator.

It's a shortcut for

density = density * invertedRatio;

Same abbreviations are possible e.g. for:

String x = "hello "; x += "world" // results in "hello world"
int y = 100; y -= 42; // results in y == 58

and so on.