ImplementingSAMBeforeJava8.java

interface ConcatStringInterface {
    String concat(String param1, String param2);
}

class ConcatStringImpl implements ConcatStringInterface {
    public String concat(String param1, String param2) {
        return param1 + param2;
    }
}

public class LambdaExpressions {
    public static void beforeJava8() {
        ConcatStringInterface concatStringInterface = new ConcatStringImpl();
	concatStringInterface.concat("a", “b”);
    }
}