public class Point {

private double xValue;
private double yValue;

public Point(double xValue, double yValue) {
    this.setxValue(xValue);
    this.setyValue(yValue);
}

public double distance(Point point) {
    double distance = Math.sqrt(Math.pow((point.getxValue() - this.xValue),
            2) + Math.pow((point.getyValue() - this.yValue), 2));
    return distance;
}

/**
 * @return the xValue
 */
public double getxValue() {
    return xValue;
}

/**
 * @param xValue
 *            the xValue to set
 */
public void setxValue(double xValue) {
    this.xValue = xValue;
}

/**
 * @return the yValue
 */
public double getyValue() {
    return yValue;
}

/**
 * @param yValue
 *            the yValue to set
 */
public void setyValue(double yValue) {
    this.yValue = yValue;
}

/*
 * (non-Javadoc)
 * 
 * @see java.lang.Object#toString()
 */
@Override
public String toString() {
    return "点(" + this.xValue + "," + this.yValue + ")";
}

/*
 * (non-Javadoc)
 * 
 * @see java.lang.Object#equals(java.lang.Object)
 */
@Override
public boolean equals(Object obj) {
    if (obj instanceof Point) {
        Point comparePoint = (Point) obj;
        return this.getxValue() == comparePoint.getxValue()
                && this.getyValue() == comparePoint.getyValue();
    }
    return super.equals(obj);
}

/**
 * 以基准点为圆心，从x轴方向逆时针旋转到基准点与point点连线经过的角度，必须保证传入点与基准点不是同一个点
 * 
 * @param point
 * @return
 */
public double getAngle(Point point) {
    if (this.getxValue() == point.getxValue()) {
        if (this.getyValue() < point.getyValue()) {
            return 90;
        } else {
            return 270;
        }
    } else if (this.getyValue() == point.getyValue()) {
        if (this.getxValue() < point.getxValue()) {
            return 0;
        } else {
            return 180;
        }
    } else {
        double kValue = (getKValue(point));
        int quadrant = getQuadrant(point);
        double angle = Math.atan(kValue) * 180 / Math.PI;
        if (quadrant != 1) {
            if (quadrant == 2 || quadrant == 3) {
                return angle + 180;
            } else {
                return angle + 360;
            }
        }
        return angle;
    }
}

/**
 * 求传入的点在调用点的哪个象限内，想对传入点的坐标平移到0，0标准坐标系下，然后通过平移后的坐标正负值进行判定
 * 
 * @param point
 * @return 返回值1，2，3，4分别代表四个象限
 */
private int getQuadrant(Point point) {
    double transPointX = point.getxValue() - this.getxValue();
    double transPointY = point.getyValue() - this.getyValue();
    if (transPointX > 0 && transPointY > 0) {
        return 1;
    } else if (transPointX < 0 && transPointY > 0) {
        return 2;
    } else if (transPointX < 0 && transPointY < 0) {
        return 3;
    } else {
        return 4;
    }
}

/**
 * 获取斜率
 * 
 * @param point
 * @return
 */
private double getKValue(Point point) {
    double kValue = (point.getyValue() - this.getyValue()) * 1.0d
            / (point.getxValue() - this.getxValue());
    return kValue;
}

public static void main(String[] args) {
    Point pointA = new Point(0, 0);
    Point pointB = new Point(0, -1);
    double angle = pointA.getAngle(pointB);
    System.out.println(pointA.toString() + "与" + pointB.toString()
            + "之间的夹角为：" + angle);
}
}