java入门的几个代码,很实用,初学者不可错过

public class SinglyLinkedList    //单向链表类
{
  protected int count;   //变量count用来标识链表长度
  protected SinglyLinkedListElement  head;   //变量head表示链表头
  public SinglyLinkedList()   //SinglyLinkedList 的构造方法
  {
    head=null;
    count=0;
  }
  public boolean isEmpty()   //方法isEmpty()的作用是判断链表是否为空
  {
    return count==0;
  }
 public void addToHead(Object value)  //方法addToHead()的作用是在链表头加入一个元素
  {
    head=new SinglyLinkedListElement(value);
    count++;
  }
  //方法removeFromHead()的作用是从链表头删除一个元素
  public Object removeFromHead()
  {if (count==0) 
return null;
    SinglyLinkedListElement temp=head;
    head=head.next();
    count--;
    return temp.value();
  }
  public Object peek()  //方法peek()的作用是取得链表头的值,不删除。
  {if (count)==0
    return null;
    return head.value();
  }
  public void addToTail(Object value)  //方法addToTail()的作用是在链表尾部加上一个结点
  {
    SinglyLinkedListElement temp=new  SinglyLinkedListElement(value,null);
    if(head!=null)
    {
      SinglyLinkedListElement finger=head;
      while(finger.next()!=null)
      {
        finger=finger.next();
      }
      finger.setNext(temp);
    }
    else head=temp;
    count++;
  }
  public Object removeFromTail() //方法removeFromTail()的作用是从链表尾部删除一个元素
  { if (count==0) 
     return null;
    SinglyLinkedListElement finger=head;
    SinglyLinkedListElement previous=null;
    while(finger.next()!=null)
    {
      previous=finger;
      finger=finger.next();
    }
    if(previous==null)
    {
      head=null;
    }
    else
    {
      previous.setNext(null);
    }
    count--;
    return finger.value();
  }
  public boolean contains(Object value) //方法contains()的作用是判断某个特定的元素是否在链表中
  {
    SinglyLinkedListElement finger=head;
    while(finger!=null && !finger.value().equals(value))
    {
      finger=finger.next();
    }
    return finger!=null;
  }
  public Object remove(Object value) //方法remove的作用是从链表中删除特定值的元素
  {
    SinglyLinkedListElement finger=head;
    SinglyLinkedListElement previous=null;
    while(finger!=null && !finger.value().equals(value))
    {  previous=finger;
      finger=finger.next();
    }
    if(finger!=null)
    {
      if(previous==null)
      {
        head=finger.next();
      }
      else
      {
        previous.setNext(finger.next());
      }
      count--;
      return finger.value();
    }
    return null;
  }
  public void clear()  //方法clear()的作用是清空链表
  {
    head=null;
    count=0;
  }
}