java实现单链表中是否有环的方法详解

package org.myorg;
public class Test{
public static boolean isExsitLoop(SingleList a) {
 Node<T> slow = a.head;
 Node<T> fast = a.head; while (fast != null && fast.next != null) {
       slow = slow.next;
       fast = fast.next.next;
            if (slow == fast)
               return true;
      }
       return false;
   }

 

public static void main(String args[]){
    SingleList list = new SingleList();
    for(int i=0;i<100;i++){
      list.add(i);
}
System.out.print(SingleList.isExistingLoop(list));
}
}

package org.myorg;
public class Node{
    public Object data; //节点存储的数据对象
    public Node next; //指向下一个节点的引用

    public Node(Object value){
        this.data = value;
   }

    public Node(){
　　　　　　this.data = null;
          this.next = null;
   }

}

package org.myorg;
public class SingleList{
    private int size;
    private Node head;

    private void init(){
        this.size = 0;
        this.head = new Node(); 
    }

   public SingleList(){
         init();
   }

  public boolean contains(Object value){
   boolean flag = false;
   Node p = head.next;
   while(p!=null){
        if(value.equals(p.data)){
           flag = true;
           break;
       }else(
            p = p.next;
           )
     }
    return flag;
  }

    public boolean add(Object value){
     if(contains(value))
         return false;
     else{
     Node p = new Node(value);
     p.next=head.next;
     head.next = p;
     size++;
}
  return true;
    }

}