Java Long Compare和ValueOf方法未定义

问题描述

我正在引用我的Java版本JDK 1.8，但仍然出现错误.这种引用有什么问题(六年后编写Java)?或任何其他更简单的方法来做到这一点?我进行了一些搜索，这些功能在更高的Java版本中可用. Eclipse是Oxygen

I am referencing my java version JDK 1.8 but I am still getting error. What is wrong with this referencing (writing Java after 6 years)? or any other simpler way to do this? I did some search and these functions are available in later java versions. Eclipse is Oxygen

对于Long类型，方法compareTo()未定义

The method compareTo() is undefined for the type Long

import java.util.Comparator;
import java.lang.Long;

public class MyComparator<Long> implements Comparator<Long>{
    @Override
    public int compare(Long long1, Long long2) {
        //Long.compareTo()
          return Long.valueOf(long1).compareTo(Long.valueOf(long2));
    }
}

和JDK指向

/Library/Java/JavaVirtualMachines/jdk1.8.0_25.jdk/Contents/Home

推荐答案

您在MyComparator的声明中声明了名称为Long的通用类型，然后又阴影 java.lang.Long.您的课程不应该是通用的.另外，您不需要Long.valueOf，因为您已经具有Long实例.更改它以删除通用名称，例如

Your declaration of MyComparator declares a generic type of name Long, and that then shadows java.lang.Long. Your class shouldn't be generic. Also, you don't need Long.valueOf since you already have Long instance. Change it to remove the generic, like

public class MyComparator implements Comparator<Long> {
    @Override
    public int compare(Long long1, Long long2) {
        return long1.compareTo(long2);
    }
}

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