了解比较器的用法

Question

while looking at a simple Comparator usage example:

Comparator<Developer> byName = new Comparator<Developer>() {
@Override
public int compare(Developer o1, Developer o2) {
    return o1.getName().compareTo(o2.getName());
}

I'm having trouble understanding this method declaration I've never seen such thing before.

In addition, I tried to do something else: I created a class that have inner classes that implement Comparator:

class Test{
class A implements Comparator<Integer> {
    @Override
    public int compare(int a, int b) {
        // Do something
    }
}


class B implements Comparator<Integer> {
    @Override
    public int compare(int a, int b) {
        return  a > b ? 1 :A.compare(a, b);
    }
}
}

A.compare(a,b) doesn't compile. It asks me to to make A and compare static but then I don't override the method compare of the comparator class.

Plus, saying I want to use the method A in another class

class C {
private int foo(){
Test.A()
}
}

it doesn't work also how do I do that properly? Any suggestions?

Answer 1

When you use a Comparator<Something> , then you are using a parameterized type (in this case: Something ).

The method signiture of compare needs to match this type.

So, try:

public int compare(Integer a, Integer b)