Answer: 0 new int[5] initializes all 5 elements to 0. Their sum is 0.

For <codeint[] a = {10, 20, 30};</code, <codea[1]</code is

Answer: 20 Index 1 is the SECOND element (20).

Answer: a is declared but not instantiated; you must allocate with new int[size] Declaring int[] a only creates a reference variable. You must allocate the array with a = new int[n] before assigning elements.

AP Computer Science A · Topic 6.1

Array Creation and Access Practice

Q: For <codeint[] a = {10, 20, 30};</code, <codea[1]</code is

Answer: 20 Index 1 is the SECOND element (20).

Q: What is wrong?

Answer: a is declared but not instantiated; you must allocate with new int[size] Declaring int[] a only creates a reference variable. You must allocate the array with a = new int[n] before assigning elements.

Part of Array.

Practice questions

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Sample questions

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Sample 1difficulty 1/5
```
int[] a = new int[5];
int sum = 0;
for (int x : a) {
  sum += x;
}
System.out.println(sum);
```
$What is printed?$
- A
  $ArrayIndexOutOfBoundsException$
- B
  $5$
- C
  $null$
- D
  $0$
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Why
$new int[5] initializes all 5 elements to 0. Their sum is 0.$
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Sample 2difficulty 2/5
$For <code> int[] a = {10, 20, 30}; </code>, <code> a[1] </code> is$
- A
  $20$
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- B
  $Out of bounds$
- C
  $10$
- D
  $30$
Why
$Index 1 is the SECOND element (20).$
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Sample 3difficulty 2/5
```
int[] a;
a[0] = 1;
```
$What is wrong?$
- A
  $Arrays cannot be declared without size$
- B
  $Index 0 is reserved$
- C
  $Nothing is wrong$
- D
  $a is declared but not instantiated; you must allocate with new int[size]$
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Why
$Declaring int[] a only creates a reference variable. You must allocate the array with a = new int[n] before assigning elements.$
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Sample 4difficulty 2/5
```
int[] a = {10, 20, 30, 40};
System.out.println(a[2]);
```
$What is printed?$
- A
  $30$
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- B
  $20$
- C
  $40$
- D
  $2$
Why
$Arrays are 0-indexed, so a[0]=10, a[1]=20, a[2]=30, a[3]=40. Index 2 is the third element, 30.$
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Sample 5difficulty 2/5
```
int[] a = {3, 1, 4, 1, 5};
System.out.println(a.length);
```
$What is printed?$
- A
  $4$
- B
  $6$
- C
  $0$
- D
  $5$
  check_circle
Why
$The initializer list has 5 elements, so a.length is 5. Note: array length uses the field a.length (no parentheses), not the method a.length().$
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