求java大神!下面是一个用java表示图的程序(邻接表表示法);在运行的时候提示NullPointerException.程序如下package graph;class Link{public int idata;public double ddata;public Link next;//.public Link(int id,double dd){
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![求java大神!下面是一个用java表示图的程序(邻接表表示法);在运行的时候提示NullPointerException.程序如下package graph;class Link{public int idata;public double ddata;public Link next;//.public Link(int id,double dd){](/uploads/image/z/14271706-10-6.jpg?t=%E6%B1%82java%E5%A4%A7%E7%A5%9E%21%E4%B8%8B%E9%9D%A2%E6%98%AF%E4%B8%80%E4%B8%AA%E7%94%A8java%E8%A1%A8%E7%A4%BA%E5%9B%BE%E7%9A%84%E7%A8%8B%E5%BA%8F%EF%BC%88%E9%82%BB%E6%8E%A5%E8%A1%A8%E8%A1%A8%E7%A4%BA%E6%B3%95%EF%BC%89%EF%BC%9B%E5%9C%A8%E8%BF%90%E8%A1%8C%E7%9A%84%E6%97%B6%E5%80%99%E6%8F%90%E7%A4%BANullPointerException.%E7%A8%8B%E5%BA%8F%E5%A6%82%E4%B8%8Bpackage+graph%3Bclass+Link%7Bpublic+int+idata%3Bpublic+double+ddata%3Bpublic+Link+next%3B%2F%2F.public+Link%28int+id%2Cdouble+dd%29%7B)
求java大神!下面是一个用java表示图的程序(邻接表表示法);在运行的时候提示NullPointerException.程序如下package graph;class Link{public int idata;public double ddata;public Link next;//.public Link(int id,double dd){
求java大神!下面是一个用java表示图的程序(邻接表表示法);在运行的时候提示NullPointerException.
程序如下
package graph;
class Link
{
public int idata;
public double ddata;
public Link next;
//.
public Link(int id,double dd)
{
idata=id;
ddata=dd;
}
//.
public void displayLink()
{
System.out.println("{"+idata+","+ddata+"}");
}
}// end class Edge
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
class graphHead
{
//int j;
Link first;
//.
public graphHead()
{
first=null;
}
//.
public boolean isEmpty()
{
return(first==null);
}
//.
public void insertFirst(int id,double dd)
{
Link newLink=new Link(id,dd);
newLink.next=first;
first=newLink;
}
}// end class graphHead
////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
public class isGraph {
public static final int N = 10;//ps:this number should be told at first
public graphHead[] ADTGraph=new graphHead[N];
//.
public void addEdge(int from,int to)
{
ADTGraph[from-1].insertFirst(to,0.0);
ADTGraph[to-1].insertFirst(from,0.0);
}
//.
public void displayGraph()
{
int i;
for(i=0;i
求java大神!下面是一个用java表示图的程序(邻接表表示法);在运行的时候提示NullPointerException.程序如下package graph;class Link{public int idata;public double ddata;public Link next;//.public Link(int id,double dd){
graphHead[] ADTGraph=new graphHead[N];
可是你数组里面 每一个graphHead都没有初始化!每一个graphHead[i]=new graphHead();