JAVA8 方法引用

// 方法一：传递代码
public class AppleComparator implements Comparator<Apple> { 
    public int compare(Apple a1, Apple a2){ 
        return a1.getWeight().compareTo(a2.getWeight()); 
    } 
}
inventory.sort(new AppleComparator());

// 方法二：实用匿名类
inventory.sort(new Comparator<Apple>() { 
    public int compare(Apple a1, Apple a2){ 
        return a1.getWeight().compareTo(a2.getWeight()); 
    } 
});

// 方法三：实用lambda表达式
inventory.sort((Apple a1, Apple a2) -> a1.getWeight().compareTo(a2.getWeight()) );
inventory.sort((a1, a2) -> a1.getWeight().compareTo(a2.getWeight()));

// 方法四：实用方法引用
inventory.sort(comparing(Apple::getWeight));  // java.util.Comparator.comparing