Java Comparator comparingInt() 例子

comparingInt( java.util.function.ToIntFunction ) 方法接受一个函数作为参数，从一个类型T中提取一个int排序键，并返回一个比较器，通过该排序键进行比较。如果指定的函数也是可序列化的，则返回的比较器是可序列化的。

语法

static <T> Comparator<T> comparingInt(ToIntFunction <T> keyExtractor)

参数： 该方法接受一个参数 keyExtractor ，它是用来提取整数排序键的函数。

返回值： 该方法返回一个比较器，通过提取的键进行比较。

异常： 如果参数为空，该方法会抛出NullPointerException。

下面的程序说明了comparingInt(java.util.function.ToIntFunction)方法：

程序1 :

// Java program to demonstrate
// Comparator.comparingInt(java.util.function.ToIntFunction)  method
  
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class GFG {
    public static void main(String[] args)
    {
  
        // create some user objects
        User u1 = new User("Aaman", 25);
        User u2 = new User("Joyita", 22);
        User u3 = new User("Suvam", 28);
        User u4 = new User("mahafuj", 25);
  
        // before sort
        List<User> list
            = Arrays.asList(u2, u1, u4, u3);
        System.out.println("Before Sort:");
        list.forEach(User
                     -> System.out.println("User age "
                                           + User.getAge()));
  
        Collections.sort(list,
                         Comparator.comparingInt(
                             User::getAge));
        System.out.println("\nAfterSort:");
        list.forEach(User
                     -> System.out.println("User age "
                                           + User.getAge()));
    }
}
class User implements Comparable<User> {
    public String name;
    public int age;
  
    public User(String name, int age)
    {
        this.name = name;
        this.age = age;
    }
  
    public int compareTo(User u1)
    {
        return name.compareTo(u1.name);
    }
  
    public String getName()
    {
        return name;
    }
  
    public void setName(String name)
    {
        this.name = name;
    }
  
    public int getAge()
    {
        return age;
    }
  
    public void setAge(int age)
    {
        this.age = age;
    }
  
    @Override
    public String toString()
    {
        return "User [name=" + name
            + ", age=" + age + "]";
    }
}

打印在IDE控制台的输出如下。

输出：

比较器 comparingInt在Java中的例子

程序2 :

// Java program to demonstrate
// Comparator.comparingInt(java.util.function.ToIntFunction)  method
  
import java.util.Arrays;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
public class GFG {
    public static void main(String[] args)
    {
  
        // before sort
        List<Order> list = Arrays.asList(
            new Order("A382y482y48", 320),
            new Order("Vvekhfbkje2", 242),
            new Order("efkhfbekjfbe", 1345),
            new Order("bhdhdfaddvad", 230),
            new Order("abkasbcjabjc", 100));
        System.out.println("Before Sort:");
        list.forEach(order -> System.out.println(order));
  
        Collections.sort(list,
                         Comparator.comparingInt(
                             Order::getValue));
        System.out.println("\nAfter Sort:");
        list.forEach(order -> System.out.println(order));
    }
}
class Order implements Comparable<Order> {
    public String orderNo;
    public int value;
  
    public int compareTo(Order o1)
    {
        return orderNo.compareTo(o1.orderNo);
    }
  
    public Order(String orderNo, int value)
    {
        super();
        this.orderNo = orderNo;
        this.value = value;
    }
  
    @Override
    public String toString()
    {
        return "Order [orderNo=" + orderNo
            + ", value=" + value + "]";
    }
  
    public String getOrderNo()
    {
        return orderNo;
    }
  
    public void setOrderNo(String orderNo)
    {
        this.orderNo = orderNo;
    }
  
    public int getValue()
    {
        return value;
    }
  
    public void setValue(int value)
    {
        this.value = value;
    }
}