Java Arrays Exercises

1. Give the total number of bytes occupied by these arrays?

1. 1. int ar[25]
   2. char M[3][4]
   3. double A[12]

Ans.

The number of bytes:

1. 1. ar[25] = 4*25 =100 bytes.
   2. M[3][4] = 2*3*4 =24 bytes
   3. A[12] = 8*12 =96 bytes

2. What is the difference between these two statements:
   1. int sum[]=new int[10]
   2. sum[1]=10;

Ans.

1. 1. Declares an integer array of size 10 having the name ‘sum’.
   2. Initialises the second element of the array ‘sum’ with 10.

3. Write the correct syntax of the following arrays:

1. 1. A1(2)
   2. Name[2,5]
   3. Roll[2;]
   4. Matrix(5)(5)

Ans.

1. 1. A1[2]
   2. Name[2][5]
   3. Roll[2]
   4. Matrix[5][5]

4. Give the proper array declaration for the following:

1. 1. Declare an integer array, which can hold 25 values.
   2. Declare a two dimensional array called mat 3×4 of integer.
   3. Declare and initialise a two dimensional array of size 5×5 to 0.

Ans.

1. 1. int a[]=new int[25];
   2. int mat[][]=new int[3][4];
   3. int a[][]={{0,0,0,0,0},{0,0,0,0,0},{0,0,0,0,0},{0,0,0,0,0},{0,0,0,0,0}};

5. Find the errors in the given program segment and re-write the statements correctly to assign values to an integer array.

int a= new int(5);
for(int i=0; i<=5; i++)
a[i]= I;

Ans.

The statement 1 has two errors: the square brackets „[ ]’ is required as “int[ ] a” or “int a[ ]”.

Also, the size of the array 5 should be within the „[ ]‟ bracket instead of ( ).

The statement 2 has one error. The loop should be 0 to 4 i.e. for( int i=0; i< 5; i++) or for( int

i= 0; i <5;i++)

Correct program code
int a[ ]= new int[ 5 ];
for(int i= 0; i <5; i++)
a[i]= i;

6. What will be the output of the following program:

class Output
{
public static void main(String args[])
{
int a[]={6,5,4,3,2,1};
int x;
for(x=5;x>=0;x--)
{
System.out.println(a[x]);
}
}
}

Ans.

1
2
3
4
5
6

7. What will be the output of the following program:

class First
{

public static void main(String args[])
{
int a[]={5,1,15,20,25};
int i,j;
int m;
i=++a[1];
j=a[2]++;
m=a[i++];
System.out.print(i+“ ”+j+“ ”+m);
}
}

Ans.

3 15 16

8. If String nam[ ]={ “simply”, “coding”, “While”, “programs”, “Boy”, “java”, “Cat”} ;.
   Write java for loop to print all the strings into different lines.

Ans.

for( int a=0; a < 7; a+ + )
{
System.out.println( nam[ a ]);
}

9. What is the output of this code:

int mat[ ][ ]= {{13,64},{77,46}};
for(int x=0;x<2;x++){
for(int y= 0; y<2; y++)
System.out.print(mat[x][y]+ " ");
System.out.println();

Ans:

13 64
77 46

10. Given the array a[ ]= {25, 58, 41, 32, 55, 30, 75, 80}; Answer the following questions.

1. 1. What are the indices of the array a[ ]?
   2. How many elements are in the array?
   3. What is the 3th element of array?
   4. Write the statement to print elements of 2nd and 6th indexes
   5. What is the start index and end index of array a[ ]

Ans.

1. 1. The indices of the array ar[ ] are 0-7
   2. Eight elements are in the array
   3. The element at 3 index is 41.
   4. System.out.printin(ar[2]+ “\t” +ar[6]);
   5. he start index is 0 and the end index is= 7

11. Write valid Java statements for the following:

1. 1. Initialize 10 integers in a single dimensional array.
   2. Initialize a double dimensional array of 3 rows and 3 columns.
   3. Initialize 7 real or decimal numbers in a single dimensional array.

Ans.

1. 1. int y[ ]= {10, 5, 6, 12, 7, 8,9, 4, 24, 88};
   2. int num[ ][ ]= {1, 2, 3}, {7, 8, 9}, {4, 5, 6}};
   3. double x[ ]= {2.0, 4.5, 6.8, 3.0, 1.1, 7.5, 9.0};

12. Consider the given array and write a valid Java program code to update each element of the array by adding 10.

int m[ ]= {4, 6, 8, 12, 16, 3, 9, 7 };

Ans.

for( int j= 0; j< m.length ; j++)
{
m[j]= m[j]+10;
}

13. What is the output of this code segment?

int G[][] = { {4, 3, 6}, {3, 4, 9}, {3, 7, 2} };
int c=0;
int arr[ ]= new int[ 9 ];
for( int j= 0; j<3; j++){
for( int h=0; h <3 ; h++){
arr[c]= G[ j ][ h ];
c++;
}
}
for (int j = 0; j <9 ; j++)
System.out.print(arr[j] + “ “);

Ans: 4 3 6 3 4 9 3 7 2

14. Given the array ar[ ]= {10, 22, 33, 44, 55. 66, 77}; Answer the following questions.

1. 1. How many elements are in the array?
   2. What are the indices of the array ar[ ]?
   3. What is the 4th element of array?
   4. Write the statement to print elements of 2nd and 4th indexes
   5. What is the start index and end index of array ar[ ]

Ans.

1. 1. Seven elements are in the array
   2. The indices of the array ar[ ] are 0-6
   3. The element at 4 index is 44,
   4. System.out.println(ar[2]+ “\t” +ar[4]);
   5. The start index is 0 and the end index is= 6

15. From the given array y[ ][ ]={{3, 4, 5},{6, 7, 8}.{1, 2, 3}}; answer the following

1. 1. Element at y[2][2]
   2. Element at y[0][1]
   3. Element at y[1][2]

Ans.

1. 1. Element at y[2][2]= 3
   2. Element at y[0][1]=4
   3. Element at y[1][2]= 8

16. If int x[]= {5,9,7,3,2,8}; What are the value of A and B?
    
    1. A= x.length
    2. B= x[3]+x[1]*x[2]

Ans.

1. 1. A=6
   2. B=66

17. Write single line statement to implement the following:

1. 1. If String nam[ ] = {“Can”, “Do”, “While”, “Text”, “Boy”, “Rat”, “Cat”);
      Count the number of names in the data structure nam.
   2. To print the string present at 4th position in string array nam[ ]
   3. To print character present at 3rd position in the string present at 2nd index.
   4. To join the strings present at 2nd and 4th position.

Ans.

1. 1. int y= nam . length;
   2. System.out.println( nam[ 4 ] );
   3. System.out.println(nam [2].charAt(3));
   4. System.out.println(nam [2].concat(nam[4]));

18. What will be the output of the following program:

class Output
{
public static void main(String args[])
{
int a,b=0;
int c[]={1,2,3,4,5,6,7,8,9,10};
for(a=0;a<10;a++)
{
if(a%2==0)
b+=c[a];
}
System.out.print(b);
}
}

In what statement, what is the output? State what the above program is doing?

Ans.

25
Adding all nos which are at even index

19. Find the syntax error(s), if any in the following program.

Class First
{
public static void main(String args[])
{
int sum[2,4];
for(i=0;i<2;i++)
{
for(j=0;j<=3;j++)
{
System.print(sum);
}
}
}
}

Ans.

class First
{
public static void main(String args[])
{
int sum[][]=new int[2][4];
for(i=0;i<2;i++)
{
for(j=0;j<=3;j++)
{
System.out.print(sum[i][j]+“ ”);
}
}
}
}

20. Identify error(s), if any, in the following program.

class First
{
public static void main(String args[])
{
int i;
int a[6]={0,1,8,7,6,4};
for(i=0;i<=a.length();i++)
System.out.println(a[i]);
}
}

Ans.

class First
{
public static void main(String args[])
{
int i;
int a[]={0,1,8,7,6,4};
for(i=0;i<a.length;i++)
System.out.println(a[i]);
}
}

21. Find the errors in the given program segment and re-write the statements correctly to assign values to an integer array.

int a= new int(8); // statement 1
for(int i=0; i<=5; i++) // statement 2
a[i]= I;

Ans.

The statement 1 has two errors: the square brackets „[ ]’ is required as “int[ ] a” or “int a[ ]”.

Also, the size of the array 5 should be within the „[ ]‟ bracket instead of ( ).

The statement 2 has one error. The loop should be 0 to 4 i.e. for( int i=0; i< 5; i++) or for( int

i= 0; i <5;i++)

Correct program code

int a[ ]= new int[ 5 ];
for(int i= 0; i <5; i++)
a[i]= i;