Comparable，hashcode和equals

说到hashcode和equals不的不想到集合类的SET,set能清楚重复的东西。

假如:

public class People {
     private String fistName;
     private String lastName;
     People(String fname,String lname){
       this.fistName = fname;
      this.lastName = lname;
   }

}

你在hashSet时想根据姓名相同的为条件来去掉重复的，重写OBJECT类的hashcode和equals一定要写对了。

public class People {
 private String fistName;
 private String lastName;
 People(String fname,String lname){
  this.fistName = fname;
  this.lastName = lname;
 }

public int hashCode(){
  return this.fistName.hashCode()*this.lastName.hashCode();
 }
 public boolean equals(Object o){  
  if( o instanceof People){
   People p = (People)o;
   if(this.fistName.equals(p.fistName)&&this.lastName.equals(p.lastName)){
    return true;
   }else{
    return false;
   }
  }else{
   return false;
  }  
 }

}

当你要对一个类做比较的时候你的实现接口compareable，实现方法public int compareTo(People o)