Basic Operations for arrays

1: Basic operation of the array

Get element: Element type variable = array name [index];

Set element: array name [index] = value;

To iterate over an array element:

for (int index = 0; Index <= nums. Length-1; index++) {

System. Out.println (nums[index]);

Array Length: array name. Length;length is a property not a method

Index range: increments from 0 onwards. [0, array name. length-1]

2: Common exceptions for manipulating arrays

nullpointerexception: null pointer exception (null reference): manipulate the array directly when the array is not initialized.

string[] bs = null;

System.out.println (Bs.length)

arrayindexoutofboundsexception : array index out-of-bounds exception.

3: Gets the maximum minimum element of the array

Get the largest element: Don't forget to pass Parameters!!!!

Public class ArrayDemo3 {

static int Getmax (int[] nums) {

int max = nums[0];

For (int index = 0; Index <= nums. Length-1; index + +)

{

If (nums[index] > Max)

{

Max = nums[index];

}

}

return max;

}

public static void Main (string[] args) {

// TODO Auto-generated method stub

int[] nums = new int[]{2,3,5,-3,4};

int max = Getmax (nums);

System. out.println (max);

}

}

4: Print array elements

When you print an array directly, the Hashcode value is printed.

static void PrintArray (string[] arr)

{

if (arr = = null)

{

System. OUT.PRINTLN ("null");

return;

}

String ret = "[";

For (int index = 0;index < arr. Length; index+ +)

{

ret = ret + arr[index];

//If the current index is not the last index, then stitch ","

if (index ! = arr.length-1)

{

ret = ret + ",";

}

}

ret = ret + "]";

System. out.println (ret);

}

In the Main method

string[] arr = {"a","B","C"};

PrintArray (arr);

5: Array elements in reverse order

Static string[] Reverse (string[] Oldarr)

{

string[] newarray = new string[Oldarr. Length]; //Create a new array to hold the inverted element

For (int index = Oldarr. Length-1;index >=0;index--)

{

newarray [Oldarr. Length-1-index] = Oldarr[index];

}

return newarray;

}

6: The element appears indexed (first/last time)

Int[] arr = {10,20,30,10,50,10,50}

Gets the index of the first occurrence of element 10 in the arr array (indexOf);

Gets the index of the last occurrence of element 10 in the arr array (lastIndexOf);

/*

* Query the location of the first occurrence of the key element in the Nums array,

Parameters

* Nums: from which array to do the query

* Key: The element of the current query

* Return: Returns the first occurrence of the index if key exists in the ARR array

* Key does not exist in the Nums array and returns -1.

*/

static int indexOf (int[] nums,int key)

{

For (int index = 0; Index <= nums. Length-1; index++)

{

If(nums[index] = = key)

{

return index;

}

}

return-1;

}

Last time

static int lastIndexOf (int[] nums,int key)

{

For (int index = nums. Length-1; index >= 0; index--)

{

If(nums[index] = = key)

{

return index;

}

}

return-1;

}

Basic Operations for arrays