java.util.Comparator使用示例

java.util.Comparator使用示例

Comparator的具体实现类

public   class  AgeComparator  implements  Comparator  {
  public int compare(Object op1, Object op2) {
    Employee eOp1 = (Employee) op1;
    Employee eOp2 = (Employee) op2;

    // 按年龄排序
    return eOp1.getAge()-(eOp2.getAge());
  }
}

public   class  NameComparator  implements  Comparator  {
  public int compare(Object op1, Object op2) {
    Employee eOp1 = (Employee) op1;
    Employee eOp2 = (Employee) op2;

    // 按姓名排序
    return eOp1.getName().compareTo(eOp2.getName());
  }
}

public   class  SalaryComparator  implements  Comparator  {
  public int compare(Object op1, Object op2) {
    Employee eOp1 = (Employee) op1;
    Employee eOp2 = (Employee) op2;

    // 按薪水排序
    return eOp1.getSalary()-(eOp2.getSalary());
  }
}

Employee类：

public   class  Employee {
  protected String name;
  protected int age;
  protected int salary;
  
  public Employee(String name,int age,int salary){
    this.name=name;
    this.age=age;
    this.salary=salary;
  }
  
  public int getAge() {
    return age;
  }
  public void setAge(int age) {
    this.age = age;
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public int getSalary() {
    return salary;
  }
  public void setSalary(int salary) {
    this.salary = salary;
  } 
}

测试：

public   class  Main {
  public static void main(String[] args){
    List<Employee> employees=new ArrayList<Employee>();
    
    employees.add(new Employee("Andy",21,2000));
    employees.add(new Employee("Felix",21,3000));
    employees.add(new Employee("Bill",35,20000));
    employees.add(new Employee("Helen",21,10000));
    employees.add(new Employee("Cindy",28,8000));
    employees.add(new Employee("Douglas",25,5000));
        
    // 按名称排序
      Collections.sort(employees,new NameComparator());
      display(employees);

      // 按年龄排序
      Collections.sort(employees,new AgeComparator());
      display(employees);
      
      // 按薪水排序
      Collections.sort(employees,new SalaryComparator());
      display(employees);
  }
  
  public static void display(List<Employee> employees){
    for(Employee e:employees){
      System.out.println("雇员名="+e.getName()+" 年龄="+e.age+" 薪水="+e.getSalary());
    }
    
    System.out.println();
  }
}

输出：

雇员名 = Andy 年龄 = 21  薪水 = 2000
雇员名 = Bill 年龄 = 35  薪水 = 20000
雇员名 = Cindy 年龄 = 28  薪水 = 8000
雇员名 = Douglas 年龄 = 25  薪水 = 5000
雇员名 = Felix 年龄 = 21  薪水 = 3000
雇员名 = Helen 年龄 = 21  薪水 = 10000

雇员名 = Andy 年龄 = 21  薪水 = 2000
雇员名 = Felix 年龄 = 21  薪水 = 3000
雇员名 = Helen 年龄 = 21  薪水 = 10000
雇员名 = Douglas 年龄 = 25  薪水 = 5000
雇员名 = Cindy 年龄 = 28  薪水 = 8000
雇员名 = Bill 年龄 = 35  薪水 = 20000

雇员名 = Andy 年龄 = 21  薪水 = 2000
雇员名 = Felix 年龄 = 21  薪水 = 3000
雇员名 = Douglas 年龄 = 25  薪水 = 5000
雇员名 = Cindy 年龄 = 28  薪水 = 8000
雇员名 = Helen 年龄 = 21  薪水 = 10000
雇员名 = Bill 年龄 = 35  薪水 = 20000