Stack类的简单应用
import java.util.Stack;public class ChartKeyManager {//最多只有4个图private static final int number = 4;private static ChartKeyManager manager = null;private Stack<Integer> unusedStack = null;private ChartKeyManager(){unusedStack = new Stack<Integer>();init();}private void init(){for( int id = number; id > 0; --id ){unusedStack.add(Integer.valueOf(id));}}public static ChartKeyManager getInstance(){if (null == manager){manager = new ChartKeyManager();}return manager;}/** * 取得一个未使用的ID，如果没有未被使用的ID，返回null * @return */public Integer useOneCompositeID(){if (!unusedStack.isEmpty()){return unusedStack.pop();}return null;}/** * 返还一个ID，这个ID恢复为可使用的ID */public void unuseOneCompositeID(Integer id){unusedStack.add(id);}public void clearAllUsedID(){unusedStack.clear();init();}
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