Java题库——Chapter6 一维数组

1)What is the representation of the third element in an array called a? 1) _______

A)a(3) B) a(2) C) a[2] D) a[3]

2)If you declare an array double[ ] list = {3.4, 2.0, 3.5, 5.5}, list[1] is ________. 2) _______

A)3.4  B)5.5  C)2.0  D)3.4  E)undefined

3)Which of the following is incorrect? (Choose all that apply.) 3) _______

A)int a = new int[2]; B)int a[ ] = new int[2];

C)int[ ] a = new int[2]; D)int a() = new int[2]; E)int[ ] a = new int(2);

4)If you declare an array double[ ] list = {3.4, 2.0, 3.5, 5.5}, the highest index in array list is ________. 4) _______

A)3 B) 2 C) 4 D) 1 E) 0

5)How many elements are in array double[ ] list = new double[5]? 5) _______

A)6 B) 5 C) 4 D) 0

6)What is the correct term for numbers[99]? 6) _______

A)array variable

B)index variable

C)array

D)indexed variable

E)index

7)Suppose int i = 5, which of the following can be used as an index for array double[ ] t = new double[100]? (Choose all that apply.) 7) _______

A)i

B)i + 10

C)(int)(Math.random() * 100))

D)Math.random() * 100

E)i + 6.5

int型整数

8)Analyze the following code.

public class Test {
  public static void main(String[ ] args) {
    int[ ] x = new int[3];
    System.out.println("x[0] is " + x[0]);
  }
}

A)The program runs fine and displays x[0] is 0.
B)The program has a runtime error because the array elements are not initialized.
C)The program has a runtime error because the array element x[0] is not defined.
D)The program has a compile error because the size of the array wasn't specified when declaring the array.

9)Which of the following statements is valid? (Choose all that apply.) 9) _______
A)char[ ] c = new char();
B)int i = new int(30);
C)int[ ] i = {3, 4, 3, 2};
D)char[ ] c = new char[4]{'a', 'b', 'c', 'd'};
E)double d[ ] = new double[30];

10)How can you initialize an array of two characters to 'a' and 'b'? (Choose all that apply.)
A)char[ ] charArray = {'a', 'b'};
B)char[2] charArray = {'a', 'b'};
C)char[ ] charArray = new char[2]; charArray = {'a', 'b'};
D)char[ ] charArray = new char[ ]{'a', 'b'};

11)What would be the result of attempting to compile and run the following code?

public class Test {
  public static void main(String[ ] args) {
    double[ ] x = new double[ ]{1, 2, 3};
    System.out.println("Value is " + x[1]);
  }
}

A)The program has a compile error because the syntax new double[ ]{1, 2, 3} is wrong and it should be replaced by new double[ ]{1.0, 2.0, 3.0};
B)The program has a compile error because the syntax new double[ ]{1, 2, 3} is wrong and it should be replaced by new double[3]{1, 2, 3};
C)The program has a compile error because the syntax new double[ ]{1, 2, 3} is wrong and it should be replaced by {1, 2, 3}.
D)The program compiles and runs fine and the output "Value is 1.0" is printed.  
E)The program compiles and runs fine and the output "Value is 2.0" is printed.  

12)Assume int[ ] t = {1, 2, 3, 4}. What is t.length? 12) ______
A)3  B) 5 C) 4 D) 0

13)Analyze the following code:

public class Test {
  public static void main(String[ ] args) {
    int[ ] x = new int[5];
    int i;
    for (i = 0; i < x.length; i++)
      x[i] = i;
    System.out.println(x[i]);
  }
}

A)The program has a compile error because i is not defined in the last statement in the main method.
B)The program displays 0 1 2 3 4.
C)The program has a runtime error because the last statement in the main method causes ArrayIndexOutOfBoundsException.
D)The program displays 4.

14)(Tricky) What is output of the following code:

public class Test {
  public static void main(String[ ] args) {
    int[ ] x = {120, 200, 016};
    for (int i = 0; i < x.length; i++)
      System.out.print(x[i] + " ");
  }
}

A)120 200 20  
B)120 200 16  
C)120 200 14   
D)016 is a compile error. It should be written as 16.

0开头表示八进制整数直接量！！！

15)In the following code, what is the printout for list2?

class Test {
  public static void main(String[ ] args) {
    int[ ] list1 = {1, 2, 3};
    int[ ] list2 = {1, 2, 3};
    list2 = list1;
    list1[0] = 0; list1[1] = 1; list2[2] = 2;
    for (int i = 0; i < list2.length; i++)
      System.out.print(list2[i] + " ");
  }
}

A)0 1 3 B) 0 1 2 C) 1 2 3 D) 1 1 1

16)In the following code, what is the printout for list1?

class Test {
  public static void main(String[ ] args) {
    int[ ] list1 = {1, 2, 3};
    int[ ] list2 = {1, 2, 3};
    list2 = list1;
    list1[0] = 0; list1[1] = 1; list2[2] = 2;
    for (int i = 0; i < list1.length; i++)
      System.out.print(list1[i] + " ");
  }
}

A)1 2 3 B) 0 1 2 C) 0 1 3 D) 1 1 1

将list1的引用赋给list2，list1和list2指向内存中的同一块区域

17)Analyze the following code:

public class Test {
  public static void main(String[ ] args) {
    int[ ] x = {1, 2, 3, 4};
    int[ ] y = x;
    x = new int[2];
    for (int i = 0; i < y.length; i++)
      System.out.print(y[i] + " ");
  }
}

A)The program displays 0 0 0 0
B)The program displays 0 0 3 4
C)The program displays 0 0
D)The program displays 1 2 3 4

18)Analyze the following code:

public class Test {
  public static void main(String[ ] args) {
    int[ ] x = {1, 2, 3, 4};
    int[ ] y = x;
    x = new int[2];
    for (int i = 0; i < x.length; i++)
      System.out.print(x[i] + " ");
  }
}

A)The program displays 0 0
B)The program displays 0 0 3 4
C)The program displays 1 2 3 4
D)The program displays 0 0 0 0

19)Analyze the following code:

public class Test {
  public static void main(String[ ] args) {
    final int[ ] x = {1, 2, 3, 4};
    int[ ] y = x;
    x = new int[2];
    for (int i = 0; i < y.length; i++)
      System.out.print(y[i] + " ");
  }
}

A)The program displays 0 0
B)The elements in the array x cannot be changed, because x is final.
C)The program has a compile error on the statement x = new int[2], because x is final and cannot be changed.
D)The program displays 1 2 3 4

20)Analyze the following code.

int[ ] list = new int[5];
list = new int[6];

A)The code can compile and run fine. The second line assigns a new array to list.
B)The code has compile errors because the variable list cannot be changed once it is assigned.
C)The code has compile errors because you cannot assign a different size array to list.
D)The code has runtime errors because the variable list cannot be changed once it is assigned.

第二行代码重新为list分配了一个新的数组

21)Analyze the following code:

public class Test {
  public static void main(String[ ] args) {
    int[ ] a = new int[4];
    a[1] = 1;
    a = new int[2];
    System.out.println("a[1] is " + a[1]);
  }
}

A)The program has a compile error because new int[2] is assigned to a.
B)The program displays a[1] is 1.
C)The program displays a[1] is 0.
D)The program has a runtime error because a[1] is not initialized.

22)The ________ method copies the sourceArray to the targetArray. 22) ______
A)System.arrayCopy(sourceArray, 0, targetArray, 0, sourceArray.length);
B)System.copyarrays(sourceArray, 0, targetArray, 0, sourceArray.length);
C)System.arraycopy(sourceArray, 0, targetArray, 0, sourceArray.length);
D)System.copyArrays(sourceArray, 0, targetArray, 0, sourceArray.length);

arraycopy方法违反了Java的命名方式，根据命名习惯，应该命名为arrayCopy。arraycopy方法没有给目标数组分配空间，复制前必须创建目标数组以及分配给它的内存空间，复制完成后，sourceArray 和 targetArray具有相同的内容。

23)When you pass an array to a method, the method receives ________. 23) ______
A)the length of the array B) a copy of the first element
C)a copy of the array D) the reference of the array

24)Show the output of the following code:

public class Test {
  public static void main(String[ ] args) {
    int[ ] x = {1, 2, 3, 4, 5};
    increase(x);
    int[ ] y = {1, 2, 3, 4, 5};
    increase(y[0]);
    System.out.println(x[0] + " " + y[0]);
  }
  public static void increase(int[ ] x) {
    for (int i = 0; i < x.length; i++)
      x[i]++;
  }
  public static void increase(int y) {
    y++;
  }
}

A)2 2 B) 1 1 C) 0 0 D) 1 2 E) 2 1

前者引用传递，后者值传递。

25)Do the following two programs produce the same result?
Program I:

public class Test {
  public static void main(String[ ] args) {
    int[ ] list = {1, 2, 3, 4, 5};
    reverse(list);
    for (int i = 0; i < list.length; i++)
      System.out.print(list[i] + " ");
  }
  public static void reverse(int[ ] list) {
    int[ ] newList = new int[list.length];
    for (int i = 0; i < list.length; i++)
      newList[i] = list[list.length - 1 - i];
    list = newList;
  }
}

Program II:

public class Test {
  public static void main(String[ ] args) {
    int[ ] oldList = {1, 2, 3, 4, 5};
    reverse(oldList);
    for (int i = 0; i < oldList.length; i++)
      System.out.print(oldList[i] + " ");
  }
  public static void reverse(int[ ] list) {
    int[ ] newList = new int[list.length];
    for (int i = 0; i < list.length; i++)
      newList[i] = list[list.length - 1 - i];
    list = newList;
  }
}

A)Yes B) No

26)Analyze the following code:

public class Test {
  public static void main(String[ ] args) {
    int[ ] oldList = {1, 2, 3, 4, 5};
    reverse(oldList);
    for (int i = 0; i < oldList.length; i++)
      System.out.print(oldList[i] + " ");
  }
  public static void reverse(int[ ] list) {
    int[ ] newList = new int[list.length];
    for (int i = 0; i < list.length; i++)
      newList[i] = list[list.length - 1 - i];
    list = newList;
  }
}

A)The program displays 1 2 3 4 5 and then raises an ArrayIndexOutOfBoundsException.
B)The program displays 1 2 3 4 5.
C)The program displays 5 4 3 2 1 and then raises an ArrayIndexOutOfBoundsException.
D)The program displays 5 4 3 2 1.

27)Analyze the following code:

public class Test1 {
  public static void main(String[ ] args) {
    xMethod(new double[ ]{3, 3});
    xMethod(new double[5]);
    xMethod(new double[3]{1, 2, 3});
  }
  public static void xMethod(double[ ] a) {
    System.out.println(a.length);
  }
}

A)The program has a compile error because xMethod(new double[3]{1, 2, 3}) is incorrect.
B)The program has a compile error because xMethod(new double[5]) is incorrect.
C)The program has a compile error because xMethod(new double[ ]{3, 3}) is incorrect.
D)The program has a runtime error because a is null.

28)The JVM stores the array in an area of memory, called ________, which is used for dynamic memory allocation where blocks of memory are allocated and freed in an arbitrary order. A)dynamic memory B) memory block C)stack D) heap

Java中的数组可以看出一个特殊的对象，声明时放在栈中，分配的空间存储在堆中。
29)When you return an array from a method, the method returns ________. 29) ______
A)the reference of the array B) the length of the array
C)a copy of the first element D) a copy of the array

30)Suppose a method p has the following heading:
public static int[ ] p()
What return statement may be used in p()? 30) ______
A)return 1; B) return new int[ ]{1, 2, 3}; C)return int[ ]{1, 2, 3}; D) return {1, 2, 3};

31)The reverse method is defined in the textbook. What is list1 after executing the following statements?
int[ ] list1 = {1, 2, 3, 4, 5, 6};
list1 = reverse(list1);
A)list1 is 6 5 4 3 2 1 B) list1 is 1 2 3 4 5 6 C)list1 is 0 0 0 0 0 0 D) list1 is 6 6 6 6 6 6

32)The reverse method is defined in this section. What is list1 after executing the following statements?
int[ ] list1 = {1, 2, 3, 4, 5, 6};
int[ ] list2 = reverse(list1);
A)list1 is 0 0 0 0 0 0 B) list1 is 6 6 6 6 6 6 C)list1 is 6 5 4 3 2 1 D) list1 is 1 2 3 4 5 6

33)Which of the following declarations are correct? (Choose all that apply.) 33) ______
A)public static void print(double... numbers, String name)
B)public static double... print(double d1, double d2)
C)public static void print(int n, double... numbers)
D)public static void print(double... numbers)
E)public static void print(String... strings, double... numbers)

34)Which of the following statements are correct to invoke the printMax method in Listing 6.5 in the textbook? (Choose all that apply.) 34) ______
A)printMax(new int[ ]{1, 2, 3});
B)printMax(1, 2, 2, 1, 4);
C)printMax(new double[ ]{1, 2, 3});
D)printMax(1.0, 2.0, 2.0, 1.0, 4.0);

35)For the binarySearch method in Section 6.9.2, what is low and high after the first iteration of the while loop when invoking binarySearch(new int[ ]{1, 4, 6, 8, 10, 15, 20}, 11)? 35) ______
A)low is 0 and high is 5
B)low is 3 and high is 6
C)low is 4 and high is 6
D)low is 0 and high is 3
E)low is 0 and high is 6

36)If a key is not in the list, the binarySearch method returns ________. 36) ______
A)insertion point B) -insertion point C)-(insertion point + 1) D) insertion point - 1

37)The selectionSort method is defined in this section. Assume list is {3.1, 3.1, 2.5, 6.4, 2.1}, what is the content of list after the first iteration of the outer loop in the method? 37) ______
A)3.1, 3.1, 2.5, 6.4, 2.1 B) 2.5, 3.1, 3.1, 6.4, 2.1 C)3.1, 3.1, 2.5, 2.1, 6.4 D) 2.1, 2.5, 3.1, 3.1, 6.4

38)The selectionSort method is defined in this section. What is list1 after executing the following statements?
double[ ] list1 = {3.1, 3.1, 2.5, 6.4};
selectionSort(list1);
A)list1 is 3.1, 2.5, 3.1, 6.4 B) list1 is 3.1, 3.1, 2.5, 6.4
C)list1 is 6.4, 3.1, 3.1, 2.5 D) list1 is 2.5 3.1, 3.1, 6.4

39)The ________ method sorts the array scores of the double[ ] type. 39) ______
A)java.util.Arrays(scores)
B)java.util.Arrays.sorts(scores)
C)Njava.util.Arrays.sortArray(scores)
D)java.util.Arrays.sort(scores)

40)Assume int[ ] scores = {1, 20, 30, 40, 50}, what value does java.util.Arrays.binarySearch(scores, 30) return? 40) ______
A)2 B) 1 C) -1 D) -2 E) 0

41)Assume int[ ] scores = {1, 20, 30, 40, 50}, what value does java.util.Arrays.binarySearch(scores, 3) return? 41) ______
A)1 B) -1 C) -2 D) 2 E) 0

binarySearch()方法的返回值为：1、如果找到关键字，则返回值为关键字在数组中的位置索引，且索引从0开始2、如果没有找到关键字，返回值为负的插入点值，所谓插入点值就是第一个比关键字大的元素在数组中的位置索引，而且这个位置索引从1开始。