cyclelink.java

循环队列的Java对象容器。

package leo.util;
/**
 * <p>是CycleObject的容器，是一个双向的循环队列，在对象中，通过CycleObject的isFirst, isLast
 * 属性来标明队列的头尾。
 * <br>可以向该容器中append, insert元素，也可以remove一个元素。</p>
 * <br>可以用在需要做轮询处理的环境中，比如一个菜单列表，可以通过按向下键来循环选择各个菜单。
 * <br><p>    CycleObject[] cycle = new CycleObject[6];
 * <br>   for (int i=0; i &lt 6; i++){
 * <br>     cycle[i] = new CycleObject(new Integer(i), "hello" + Integer.toString(i));
 * <br>   }
 * <br>   CycleLink link = new CycleLink(cycle);
 * <p>Copyright: Copyright (c) 2004</p>
 * <p>Company: </p>
 * @author Smilingleo
 * @version 1.0
 */
public class CycleLink {
  private static int size = 2;
  private CycleObject[] cycle;
  private int currentPos = 0;
  public CycleLink(CycleObject[] cycle) {
    this.size = cycle.length;
    this.cycle = new CycleObject[size];
    this.cycle = cycle;
    sort(cycle);
  }
  /**
   * 如果是空的，插入第一个，如果非空取最后一个，然后设置顺序
   * @param last CycleObject
   */
  public void append(CycleObject last){
    CycleObject[] temp = new CycleObject[size + 1];
    for(int i=0; i<size; i++){
      temp[i] = cycle[i];
    }
    temp[size] = last;
    sort(temp);
    cycle = temp;
  }
  /**
   * 在pos位置上插入一个新的可轮询对象。
   * @param obj CycleObject
   * @param pos int
   * @throws Exception 在pos值小于零，大于队列长度时抛出异常。
   */
  public void insert(CycleObject obj, int pos) throws Exception{
    if (pos < 0 || pos > cycle.length) throw new Exception("插入位置参数错误");
    size++;
    CycleObject[] temp = new CycleObject[size];
    for(int i=0; i<pos; i++){
      temp[i] = cycle[i];
    }
    temp[pos] = obj;
    for (int i=pos+1; i<size; i++){
      temp[i] = cycle[i - 1];
    }
    sort(temp);
    cycle = temp;
  }
  /**
   * 从队列中删除一个可轮询对象
   * @param obj CycleObject
   * @throws Exception 在队列中没有该对象时抛出异常。
   */
  public void remove(CycleObject obj) throws Exception{
    for (int i=0; i<cycle.length; i++){
      if (cycle[i] == obj){
        remove(i);
        return;
      }
    }

  }
  /**
   * 将队列中第pos个元素删除。
   * @param pos int
   * @throws Exception 在pos小于0,大于队列长度时抛出异常。
   */
  public void remove(int pos) throws Exception{
    if (pos < 0 || pos > cycle.length) throw new Exception("待删除元素的位置参数错误");
    if (cycle.length == 1){
      cycle = new CycleObject[1];
      return;
    }
    CycleObject[] temp = new CycleObject[cycle.length - 1];
    for (int i=0; i<pos; i++)
      temp[i] = cycle[i];
    for (int i=pos; i<cycle.length - 1; i++){
      temp[i] = cycle[i + 1];
    }
    sort(temp);
    cycle = temp;
  }
  /**
   * 将整个队列根据CycleObject[]数组的顺序重新进行排序，重新设定上下关系，重新设定头、尾位置。
   * @param cycle CycleObject[]
   */
  public void sort(CycleObject[] cycle){
    size = cycle.length;
    for (int i=0;i<size;i++){
      if (i > 0) cycle[i].setPrior(cycle[i - 1]);
      if (i < size - 1) cycle[i].setNext(cycle[i + 1]);
      cycle[i].setFirst(false);
      cycle[i].setLast(false);
    }
    if (size > 0){
      cycle[0].setPrior(cycle[size - 1]);
      cycle[size - 1].setNext(cycle[0]);
      cycle[0].setFirst(true);
      cycle[size - 1].setLast(true);
    }
  }
  public CycleObject[] getCycleLink(){
    return cycle;
  }
  /**
   * 返回当前第index个元素，游标不受影响。
   * @param index int
   * @return CycleObject
   */
  public CycleObject getCycleObject(int index){
    return cycle[index];
  }
  public int size(){
    return cycle.length;
  }
  public int getIndex(Object id){
    for (int i=0; i<cycle.length; i++){
      if (cycle[i].getKey().equals(id))
        return i;
    }
    return 0;
  }
  public CycleObject get(Object id){
    for (int i=0; i<cycle.length; i++){
      if (cycle[i].getKey().equals(id)){
        return cycle[i];
      }
    }
    return null;
  }
  /**
   * 先生成一个空白的容器对象，然后再添加满足条件的
   * @param id String
   * @return CycleLink
   */
  public CycleLink filte(String id){
    if (id.length() == 0) return this;
    CycleObject[] temp = new CycleObject[0];
    CycleLink result = new CycleLink(temp);
    for (int i=0; i<cycle.length; i++){
      if (cycle[i].getKey().toString().startsWith(id)){
        result.append(cycle[i]);
      }
    }
    if (result.size() == 0)
      return null;
    return result;
  }
  /**
   * 查找CycleObject[]中第一个key与id相符的元素位置。
   * @param id String
   * @return int 如果能查到，返回其位置，如果查不到，返回-1
   */
  public int findFirst(String id){
    if (id.length() == 0) return 0;
    for (int i=0; i<cycle.length; i++){
      if (cycle[i].getKey().toString().startsWith(id)){
        return i;
      }
    }
    return -1;
  }
  public CycleLink clone(){
    CycleObject[] temp = new CycleObject[cycle.length];
    for (int i=0; i<cycle.length; i++){
      temp[i] = new CycleObject(cycle[i].getKey(), cycle[i].getValue());
    }
    CycleLink cloned = new CycleLink(temp);
    return cloned;
  }
  public CycleObject getCurrentObject(){
    return getCycleObject(currentPos);
  }
  public void moveForward(){
    currentPos = (currentPos == (cycle.length-1))?0:(currentPos + 1);
  }
  public void moveBackward(){
    currentPos = (currentPos == 0?(cycle.length - 1):(currentPos - 1));
  }
  public int getCurrentPos(){
    return currentPos;
  }
  public void moveToPos(int pos){
    currentPos = pos;
  }
}