This issue is reproducible in macOS with Japanese Keyboard input. The application contains multiple java.awt.TextField().

Steps to reproduce:

1. Switch keyboard layout to Japanese Hiragana.
2. In the 1st text field, press ‘a’ key on the keyboard twice.
(In Japanese it is ‘ああ’)
3. Click the 2nd text field and press ‘b’ key once.
It should show ‘b’ only in the 2nd text field, but it shows ‘ああb’.
4. Click the 3rd text field and press ‘c’ key once.
It should show ‘c’ only in the 3rd text field, but it shows ‘ああbc’.

The compositing text of text field gets copied to the next text field. Moving the focus with a mouse click from one text field to another should stop composition and not copy its state to another text component.

The issue is not reproducible with English Keyboard input.