3. Write a function that accepts a character array, a zero-based start position and a length. It should return a character array containing containing lengthcharacters starting with the startcharacter of the input array. The function should do error checking on the start position and the length and return null if the either value is not legal. The function signature is: char[ ] f(char[ ] a, int start, int len)

Examples

if input parameters are	return
{a, b, c}, 0, 4	null
{a, b, c}, 0, 3	{a, b, c}
{a, b, c}, 0, 2	{a, b}
{a, b, c}, 0, 1	{a}
{a, b, c}, 1, 3	null
{a, b, c}, 1, 2	{b, c}
{a, b, c}, 1, 1	{b}
{a, b, c}, 2, 2	null
{a, b, c}, 2, 1	{c}
{a, b, c}, 3, 1	null
{a, b, c}, 1, 0	{}
{a, b, c}, -1, 2	null
{a, b, c}, -1, -2	null
{}, 0, 1	null

by java