Introduction to arrays -- array

Java Array

Arrays are one of the most important data structures for every programming language , Of course, the implementation and processing of arrays are different in different languages .

Java The array provided in the language is used to store fixed size elements of the same type .

You can declare an array variable , Such as num[10] Instead of a direct statement 10 Independent variables num0,num1,....,num10.

Declare array variables

data type [] Array name ; perhaps data type Array name [];

int[] nums1;

or

int nums1[];

Be careful :  It is recommended to use int [] nums1;  Declare array variables in a declaration style . int  nums1[]; Style comes from C/C++ Language , stay Java In order to make C/C++ Programmers can quickly understand java Language .

Create array

Java Language use new To create an array , The grammar is as follows ：

Declare a length of 5 Of int An array of types

int[] nums1 = new int[3];

Assign value to array  

Array name [ Subscript ] = data ;

int[0]=1;

int[1]=2;

int[2]=3;

Operational data , Use array names [ Array element subscript ] To manipulate data  

Change the first element of the array into 1000：

nums1[0] = 1000;
System.out.println(nums1[0]);

java There is 8 Array of large basic types  

Each has its own default value ：

byte[] nums1;// The default value is 0
short[] nums2;// The default value is 0
int[] nums3;// The default value is 0
long[] nums4;// The default value is 0
float[] nums5;// The default value is 0.0
double[] nums6;// The default value is 0.0
char[] chars;// The default value is ： Space  
boolean[] bools;// The default value is false

java Nissan definition arrays are mostly abbreviated  

1. data type [] Array name = new data type []{ data 1, data 2,...., data n};
2. data type [] Array name = { data 1, data 2,...., data n};

// Declare a length of 5 Of int Type array , The data inside are 11 25 36 98 75
int[] nums = new int[]{11,25,36,98,75};

// Declare a length of 5 Of char An array of types , The elements inside are 'a'  'f'  '3'  'm' 'r'
char[] chars = {'a','f','3','m','r'}; 

Traversal of array  

Every element in the array can be accessed by index . The index of the array is usually from 0 Start , That is, the index of the first element in the array is 0. The last element of the array is located in （n-1) An index . We call it based on 0 The index of . Arrays can also be based on other numbers , We call it based on n The index of .

Use for Simply loop through all indexes in the array , You can access all the elements in the array .
 

	public static void main(String[] args) {
//		 Define a sum Array 
		int[] sum={1,5,6,8};
//		 Traverse 
		for (int i = 0; i < sum.length; i++) {
			System.out.print(sum[i]+" ");
		}
	}

Running results ：

 

For-Each loop

JDK 1.5 Introduced a new type of cycle , go by the name of For-Each Cycle or enhanced cycle , It can traverse arrays without subscripts .

The syntax is as follows ：

for(type element: array)
{
    System.out.println(element);
}

	public static void main(String[] args) {
//		 Define a sum Array 
		int[] sum={1,5,6,8};
//		 Traverse 
		/*for (int i = 0; i < sum.length; i++) {
			System.out.print(sum[i]+" ");
		}*/
		for (int i : sum) {
			System.out.print(i+" ");
		}
	}

  The result is the same ：