Java中静态变量的适用场景

    Java类中的静态变量在程序运行期间，其内存空间对所有该类的对象实例而言是共享的，有些时候可以认为是全局变量。因此在某些时候为了节省系统内存开销、共享资源，可以将类中的一些变量声明为静态变量，通过下面的例子，你可以发现合理应用静态变量带来的好处：
/**
 * @author Administrator
 */
public enum FaxTemplate {
   酒店通知单, 机票催票, 度假通知;

 

 

 

 Map<String, Position> variablePositions = new HashMap<String, Position>();
 Map<String, CollectionPosition> collectionPositions = new HashMap<String, CollectionPosition>();

 String templatePath;
 String resultPath;
 String name;
 String file;

 

 

 public FaxTemplate setCollection(String name, String rowRange) {
  

collectionPositions.put(name, new CollectionPosition(rowRange));
  return this;
 }

 

 public FaxTemplate setCollectionColumn(String collectionName,
   String cellName, String strVal) {
  collectionPositions.get(collectionName).set(cellName,
    Integer.parseInt(strVal));
  return this;
 }

 

public static class CollectionPosition {
  public RowRange rowRange;
  public Map<String, Integer> cells = new HashMap<String, Integer>();

  public CollectionPosition(String rowRange) {
   this.rowRange = new RowRange(rowRange);
  }

  public CollectionPosition set(String cellName, Integer val) {
   cells.put(cellName, val);
   return this;
  }

  public Integer get(String cellName) {
   return cells.get(cellName);
  }
 }

 public static class RowRange {
  public int start;
  public int end;

  public RowRange(String strVal) {
   String[] strs = strVal.split(",");
   this.start = Integer.parseInt(strs[0]);
   this.end = Integer.parseInt(strs[1]);
  }
 }

 public static class Position {
  public int row;
  public int col;

  public Position(int row, int col) {
   this.row = row;
   this.col = col;
  }

  @Override
  public boolean equals(Object obj) {
   if (obj == null) {
    return false;
   }
   if (getClass() != obj.getClass()) {
    return false;
   }
   final Position other = (Position) obj;
   if (this.row != other.row) {
    return false;
   }
   if (this.col != other.col) {
    return false;
   }
   return true;
  }

  @Override
  public int hashCode() {
   int hash = 7;
   return hash;
  }

 }
}