java sort

一：Arrays.sort(int[] a )

二：Collections.sort(List)
   
   Collections.reverse(list);

public class Test1 {
  
  public static void main(String[] args) {
    
  List<Dog> list = new ArrayList<Dog>();
 
  list.add(new Dog(1));
  list.add(new Dog(3));
  list.add(new Dog(4));
  list.add(new Dog(2));
  list.add(new Dog(5));
  list.add(new Dog(6));
 
Collections.sort(list);
 
  for(Dog dog : list){
  System.out.println(dog.getAge());
  }
 
  List<String> list = new ArrayList<String>();
 
  list.add("a");
  list.add("c");
  list.add("b");
 
  Collections.sort(list);
  for(String s : list){
  System.out.println(s);
  }
  }
}


public class Dog implements Comparable {
 
private int age;
public int getAge() {
return age;
}

public void setAge(int age) {
this.age = age;
}

public Dog(){}
public Dog( int age){

this.age = age;
}
  
@Override
public int compareTo(Object o) {

Dog dog = (Dog)o;
if( null == o){

return -2;
}
if(this.getAge() > dog.getAge()){
return 1;

}else if( this.getAge() == dog.getAge()){

return 0;
}


return -1;


}
}