SCJP exam. The most common "Compilation fails" questions-2

no default constructor in a superclass

class One{
    String s;
    One(String s){
        this.s = s;
    }
}
class Two extends One{
    Two(String s){
                   // problem 
        this.s = s;
    }
}

interface implementation (method signature)

class Persons{
    String name;
    Persons(String name){
        this.name = name;
    }
    public String toString() {
        return this.name;
    }
}
interface Personable {
    Persons getPerson(String name);
}
class MyPerson implements Personable{
    Persons getPerson(String name) { // problem (must be public)
        return new Persons(name);
    } 
    public static void main(String[] args){
        List ps = new ArrayList();
        MyPerson m = new MyPerson();
        for (int i = 100; i++ < 102; ps.add(m.getPerson("" + i)));
        for(Object o:ps) System.out.println(o);
    }
}

SCJP exam. The most common "Compilation fails" questions

Illegal package declaration (looks like import statement).

package com.mypackage.classes.*;  // problem

Out of scope of visibility

class OutOfScopeTest{
    static int x;
    public static void main(String[] args){
        for(int i = 0; i < 10; i++){
            x++;
        }
        System.out.println(x + i); // problem
    }
}

All local variables must be initialized before using.

class LocalVariableTest{
    public static void main(String[] args){
        Boolean b;
        if(b == null){ // problem
            b = false;
        }else{
            b = true;
        }    
    }
}

No enum declaration within any method's scope. 
Enum types must not be local.

class A {
    public static void doStuff(){
        enum Sex {MALE, FEMALE, SHEMALE}; // problem
        Sex sex = Sex.MALE;
    }
}

MasterExam (SCJP 6). Sorting with a Comparator

From first attempt I didn't answer correctly. I leave this question for my memories.
Original code example:

package mastertest.sort;
import java.util.Arrays;
import java.util.Comparator;

public class Sort {

    public static void main(String[] args) {
        String [] words = {"Good","Bad", "Ugly"};
        java.util.Comparator<String> best = new Comparator<String>(){
            public int compare(String s1, String s2){
                return s2.charAt(1) - s1.charAt(1);
            }
        };
        Arrays.sort(words,best);
        System.out.println(words[0]);
    }
}