First Stage 10 array

Array

(a) array:

　　　　An array is a collection of ordered data, and each element in the array has the same array name and subscript to uniquely determine the elements in the array.

　　　

(ii) One-dimensional array declaration:

　　　　　Type [] array;

Type array[];

　　　Note:

Recommended for use in Java: type [] array;

1. An array is an object

2. Declaring an array does not create an object

3. Do not specify the length when declaring

　　

　　To create an array:

Create an array of basic data types: int[] i = new int[2];

Create an array of reference data types: student[] s = new student[100];

After an array is created, the elements have an initial value

　　　　

Type default value

BYTE 0

Short 0

int 0

Long 0l

Float 0.0f

Double 0.0d

Char \u0000

Boolean false

Reference types NULL

Initialize the array:

Declaration, creation, initialization separation;

Int[] I; Defining arrays

i = new int[2]; Allocate space

I[0] = 0; Initialization

I[1] = 1;

　　　　

Declare, create, initialize at the same time:

Int[] i = {0,1};//display initialization {} There are several values, the array length is a few

(iii) two-dimensional arrays

Format 1:int[] [] i1 = new Int[2][3];

Defines a two-dimensional array called I1

2 One-dimensional arrays in a two-dimensional array

3 elements in each one-dimensional array

The names of one-dimensional arrays are i1[0],i[1]

Assigning a value of 7 to the first one-dimensional array of 1 feet is i1[0][1]=7;

Format 2:int[] [] i2 = new int[3][];

3 one-dimensional arrays in a two-dimensional array

Each one-dimensional array is a default initialization value of NULL

These three one-dimensional arrays can be initialized individually

I2[0] = new INT[3];

I2[1] = new INT[1];

I2[2] = new INT[2];

Format 3:int[[] arr = {{3,8,2},{2,7},{9,0,1,6}};

Define a two-dimensional array named arr

Three one-dimensional arrays in a two-dimensional array

The specific elements in each one-dimensional array are also initialized

The first one-dimensional array of arr[0]={3,8,2};

The second one-dimensional array of arr[1]={2,7};

The third one-dimensional array arr[2]={9,0,1,6};

The length representation of the third one-dimensional array: arr[2].length;

　　　　

　　　　　　　

First Stage 10 array