As Frisch commented, Java apps runs in a virtual machine. No JVM I know of has implemented DRM to suppress screen-shots.
And the issue is moot. Most everybody nowadays carries a phone in their pocket or purse. Those phones are equipped with a high-resolution camera capable of taking digital images of any screen.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…