Use Japanese locale. Patch up 2D so it can display Japanese text:
$ export JAVA_FONTS=/net/fonts/a/fonts/unicode
Run SwingSet:
$ cd /usr/local/java/jdk1.2fcs/solaris/demo/jfc/SwingSet
$ /usr/local/java/jdk1.2fcs/solaris/bin/java SwingSet
Go to Plain Text pane. Click into Text Area until it accepts typing. Turn on Japanese input (Control-Space), type some text (e.g., "nihon"), but do not convert or commit (the text should be shown white-on-black). Use the mouse to select a different section of the text in the Text Area. The section will be highlighted. Type Control-W. As the conversion starts, the composed text jumps to replace the selected text.

What should happen: When the user clicks into a different part of the text, the composed text should be committed, it should stay in the location where it was typed.