Please Explain Java 8 Method Reference to instance Method using class name

Question

public interface MyFunc {

    boolean func(T v1, T v2);

}

public class HighTemp {

    private int hTemp;

    HighTemp(){

           


        

Answer 1

This is the Interface

package learninglambdaexp;

@FunctionalInterface
public interface TempInterface {

    public boolean validTemp(Temperature temp);
}

This is the class

package learninglambdaexp;

public class Temperature {

    private int temp;

    public Temperature(int temp) {
        this.temp = temp;
    }

    public boolean isEvenTemp() {
        return temp % 2 == 0;
    }

    public boolean isOddTemp(){
    return !isEvenTemp();
    }
}

This is the Class with the Main Method

package learninglambdaexp;

import java.util.ArrayList;
import java.util.List;

public class AnotherMainClass {

    public static void main(String[] args) {

        List tempCollection = new ArrayList<>();
        tempCollection.add(new Temperature(100));
        tempCollection.add(new Temperature(20));
        tempCollection.add(new Temperature(30));
        tempCollection.add(new Temperature(40));
        tempCollection.add(new Temperature(50));
        tempCollection.add(new Temperature(60));
        tempCollection.add(new Temperature(70));
        int k1 = countVariation(tempCollection, Temperature::isEvenTemp);
        //int k2 = countVariation(Temperature::lowTemp);
        System.out.println(k1);
        // System.out.println(k2); 
    }

    private static int countVariation(List tempCollection, TempInterface ti) {
        int count = 0;
        for (Temperature eachTemp : tempCollection) {
            if (ti.validTemp(eachTemp)) { // (eachTemp) -> {return eachTemp.isEvenTemp();};
                count++;
            }
        }
        return count;
    }
}

With one argument its easier to understand