Java中的比较器比较Int（）与示例

compareInt(Java.util.function .ToIntFunction )方法接受一个函数作为参数，该函数从类型 T 中提取一个 int 排序键，并返回一个按该排序键进行比较的比较器。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可序列化的。

句法：

static  Comparator comparingInt(ToIntFunction  keyExtractor)

参数：此方法接受单个参数keyExtractor ，它是用于提取整数排序键的函数。

返回值：此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，此方法将抛出 NullPointerException。

下面的程序说明了 compareInt(Java 函数.ToIntFunction) 方法：
方案一：

// 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 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 {
    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 控制台上的输出如下所示。
输出：

方案二：

// 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 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 {
    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;
    }
}

控制台上打印的输出如下所示。
输出：

参考资料： https: Java Java 函数)