★★★★JaVa 选择题★★★★ - Java / Java SE

Question 1 (1 mark) 
Which of the following are valid method headers ? 
 A public static int[] meth(int[] x) 
 B public static int meth(int[] x) 
 C public static int meth(int x) 
 D public static int[] meth(int x) 

 
  Question 2 (1 mark) 
In the following code C is a subclass of B and B is a subclass of A. Which of these must be declared abstract ? 
class A {
  public abstract void addOne();
  protected int x; 
}
class B extends A{
  protected int y; 
}
class C extends B {
  public void addOne() {
  x++; 
  y++;  
  }
}
 
 A B 
 B A 
 C C 

 
  Question 3 (1 mark) 
In the SomeOtherClass method increment(), which of the statements below are valid ? (choose all) 
class A {
…
  private int a;
  int b;
  protected int c;
  public int d;

}
class SomeOtherClass { // not in same package
  void increment() {
  A refA = new A(...);
  // statements to be inserted here

  }
}
 
 A refA.b++ 
 B refA.d++ 
 C re