btEqual.setOnAction(new EventHandler<ActionEvent>() {
public void handle(ActionEvent event) {
ScriptEngineManager manager = new ScriptEngineManager();
ScriptEngine SE = manager.getEngineByName("js");
String string = new String(showExpression.getText());
try {
String ans = SE.eval(string).toString();
showExpression.setText(ans);
} catch (Exception e) {
// TODO: handle exception
showExpression.setText("ERROR!");
}
}
});
异常处理，就是里面可能会出现运行时异常，比如空指针异常，类型转换异常等。所以为了保证程序正常运行，就需要处理。