Q:

What does ~ means in Java?

Searching on the documentation of Node in JavaFX i walked through this method:
     /**
     * Set all dirty bits
     */
    private void setDirty() {
        dirtyBits = ~0;
    }

   //where dirtyBits is an int

I have searched on search engine but can't find what ~ means?

A:

Is a the unary bitwise operator, changes in binary each 0 by 1 and each 1 by 0
From documentation

The unary bitwise complement operator "~" inverts a bit pattern; it can be applied to any of the integral types, making every "0" a "1" and every "1" a "0".
For example, a byte contains 8 bits; applying this operator to a value whose bit pattern is 00000000 would change its pattern to 11111111.

As stated in comments, problem of this is not lack of effort by user either documentation but problem of the search engines like google because remove punctuation symbols (like ~) when searching.
For people like me, non English native speakers is a real problem sometimes to find the correct words. In order to avoid this, in this case, you can  search java bitwise operator for further info.

