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我在下面开发了使用比较器的..

这是我的pojo..

  class Emp
{
      String name,job;
      int salary;
      public Emp(String n,String j,int sal)
      {
         name=n;
         job=j;
         salary=sal;
       }
      public void display()
      {
        System.out.println(name+"\t"+job+"\t"+salary);
       }
      public boolean equals(Object o)
      {
          Emp p=(Emp)o;
          return this.name.equals(p.name)&&this.job.equals(p.job)    &&this.salary==p.salary;
       }
       public int hashCode()
       {
          return name.hashCode()+job.hashCode()+salary;
       }  

}

这是我的用户定义的集合类集合..

  ArrayList list=new ArrayList();
          list.add(new Emp("Ram","Trainer",34000));
          list.add(new Emp("Sachin","Programmer",24000));
          list.add(new Emp("Priyanka","Manager",54000));
          list.add(1,new Emp("Ravi","Administrator",44000));
          list.add(new Emp("Anupam","Programmer",34000));
          list.add(new Emp("Sachin","Team Leader",54000));
          System.out.println("There are "+list.size()+" elements in the list.");
          System.out.println("Content of list are : ");
         ListIterator itr=list.listIterator();
          System.out.println("Sort Object according to Salary");
         Collections.sort(list,new SalaryComparator());
         System.out.println("Content of list are : ");
          itr=list.listIterator();
          while(itr.hasNext())
          {
            Emp e=(Emp)itr.next();  
            e.display();
          }
      }

最后是我的比较器类 

class SalaryComparator
  implements Comparator
{
  public int compare(Object paramObject1, Object paramObject2)
  {
    Emp localEmp1 = (Emp)paramObject1;
    Emp localEmp2 = (Emp)paramObject2;
    return localEmp1.salary - localEmp2.salary;
  }
}

现在仪式是根据薪水按递增顺序排序，但请建议我如何在比较器中实现逻辑，以便首先根据薪水排序，然后根据工作，即先薪水然后工作，请建议。

4

2 回答 2

1

您始终可以在比较器函数中包含多重比较。在这种情况下：

class SalaryComparator
  implements Comparator
{
  public int compare(Object paramObject1, Object paramObject2)
  {
    Emp localEmp1 = (Emp)paramObject1;
    Emp localEmp2 = (Emp)paramObject2;
    int salaryDiff = localEmp1.salary - localEmp2.salary;
    if (salaryDiff != 0) {
      return salaryDiff;
    } else {
      if (localEmp1.job == null) {
        if (localEmp2.job == null) {
          return 0;
        } else {
          return 1;
        }
      } else {
        if (localEmp2.job == null) {
          return -1;
        } else {
          return localEmp1.job.compareTo(localEmp2.job);
        }
      }
    }
  }
}

这种空值检查设置将没有作业值的 Emp 实例置于字母排序的末尾。

于 2012-05-07T17:18:29.720 回答
0

您可以使用泛型使您的代码更安全：

import java.util.*;

class Emp
// as is

// use Comparator <Emp> 
class SalaryComparator implements Comparator <Emp>
{
    // 'Emp' as param type, no casting or isinstanceof inside
    public int compare (Emp emp1, Emp emp2)
    {
        int diff = emp1.salary - emp2.salary;
        if (diff != 0) return diff; 
        else return (emp1.job.compareTo (emp2.job));
    }
}

public class EmpTest 
{
    public static void main (final String args[])
    {
        // how to use collections generically should be known by now:
        ArrayList <Emp> list = new ArrayList <Emp> ();
        list.add (new Emp ("Ram","Trainer", 34000));
        // ...

        // position 3 - slightly more complicated here ...
        ListIterator <Emp> itr = list.listIterator ();
        // ...
        while (itr.hasNext ())
        {
                // but simpler here:
            Emp e= itr.next ();  
            e.display ();
        }
    // here you could use the simplified for-loop:
    for (Emp e : list)
    {
        e.display ();
    }
    }
}
于 2012-05-07T17:41:40.087 回答