java - 有没有办法摆脱我得到的这个空指针异常？

Question

以下代码显示了空指针异常

private void _settooltip() {
    localXYLineAndShapeRenderer.setBaseToolTipGenerator(new XYToolTipGenerator() {
        @Override
        public String generateToolTip(XYDataset dataset, int series, int item) {
                //String toolTip = getToolTipText();
                   // return toolTip;
            CurveSegment segment = (CurveSegment) curveEncapsulator.getSegment(currentCurve);
            if (segment != null) {
                segment.getA();
                segment.getB();
                segment.getC();
            }


            double A = segment.getA();
            double B = segment.getB();
            double C = segment.getC();


            String AA = String.valueOf(A);
            String BB = String.valueOf(B);
            String CC = String.valueOf(C);


            return "A = " + AA + " B = " + BB + " C = " + CC;



        }
    });
}

我正在异常(exception)

public String generateToolTip(XYDataset数据集，int系列，int项)

谁能告诉我如何处理此空指针异常？

Answer 1

该错误可能与“段”有关，您可以像这样尝试sthg；

        double A = 0;
        double B =  0;
        double C =  0;

        String AA =  "";
        String BB =  "";
        String CC =  "";

        if (segment != null) {
            A = segment.getA();
            B = segment.getB();
            C = segment.getC();

            AA = String.valueOf(A);
            BB = String.valueOf(B);
            CC = String.valueOf(C);
        }

如果您共享stck trace，我们可以提供更好的帮助。