答案（1）

1）select Fclass, max(Fscore) from table group by Fclass, Fid;

2）单例模式

public class Singleton{
  /* 懒汉式 */
  private static Singleton instance = new Singleton();
  
  private Singleton(){}
  
  public static Singleton getInstance(){
    return instance;
  }
}

public class Singleton{
  /* 饿汉式 */
  private static Singleton instance = null;
  
  private Singleton(){}
  
  public static Singleton getInstance(){
    if(instance == null)
        instance = new Singleton();
    return instance;
  }
}

 3）冒泡排序

public void BubbleSort(int[] a, int n){
  boolean change = true;
  for(int i = 1; i < n && change; i++){
    change = false;
    for(int j = 0; j < n - i; j++){
      if(a[j] > a[j + 1]){
        int t = a[j];
        a[j] = a[j + 1];
        a[j + 1] = t;
        change = true;
      }
    }
  }
}

 4）DOM、SAX、JDOM、DOM4J

public class HrReader {
  public void readXml() {
    String inputXml = "E:/hr.xml";
    SAXReader saxReader = new SAXReader();
      try {
        Document document = saxReader.read(inputXml);
        Element root = document.getRootElement();
        List<Element> employees = root.elements("employee");
          for (Element employee : employees) {
            Attribute att = employee.attribute("no");
            System.out.print(att.getText() + " ");
            
            System.out.print(employee.elementText("name") + " ");
            System.out.print(employee.elementText("age") + " ");
            System.out.print(employee.elementText("salary") + " ");
            
            Element department = employee.element("department");
            System.out.print(department.element("dname").getText() + " ");
            System.out.println(department.element("address").getText());
          }
      } catch (DocumentException e) {
          e.printStackTrace();
        }
  }

  public static void main(String[] args) {
    HrReader hrReader = new HrReader();
    hrReader.readXml();
  }
}