有一个接口
public interface Rtriangle {
int getApexX1();
int getApexY1();
int getApexX2();
int getApexY2();
int getApexX3();
int getApexY3();
}
还有一个实现这个接口的类
public class RightTriangle implements Rtriangle{
private Point a;
private Point b;
private Point c;
public RightTriangle (int x1, int y1, int x2, int y2, int x3, int y3){
this.a.x=x1;
this.a.y=y1;
this.b.x=x1;
this.b.y=y1;
this.c.x=x1;
this.c.y=y1;
}
public int getApexX1(){
return a.x;
}
public int getApexY1(){
return a.y;
}
public int getApexX2() {
return b.x;
}
public int getApexY2(){
return b.y;
}
public int getApexX3(){
return c.x;
}
public int getApexY3(){
return c.y;
}
}
还有一个使用这个类的类:
public class RtriangleProvider {
public static Rtriangle getRtriangle(){
try{
Rtriangle tr = new RightTriangle(0, 0, 0, 2, 2, 0);
return tr;
}
catch(Exception e){
System.out.print(e.toString());
return null;
}
}
}
当我尝试使用 getRtriangle() 方法时,我在这一行得到 NullPointerException 异常:
Rtriangle tr = new RightTriangle(0, 0, 0, 2, 2, 0);
关于 RightTriangle 创建。
public class TestTriangle {
@Test
public void testRight(){
Rtriangle tr =RtriangleProvider.getRtriangle();
}
}
我不明白构造函数有什么问题。我将不胜感激任何建议。