“This is the second day of my participation in the Gwen Challenge in November. See details: The Last Gwen Challenge in 2021”

First, the concept of arrays

A collection of data of the same type. An array is just a container. There’s a lot of data involved in the operation, so what’s the first thing you need to do. Rather than how to operation how to save the data so that the later operation, then an array is a way to store the data, where you can save data we call it the container, the container is filled with an array of elements, can hold any type of data array, although you can install any type of data, but can only be defined array with one element, That is, once an array is defined, the type of data stored in it is determined. What’s the difference between saving data and not saving data? The great thing about arrays is that they automatically number all the elements they store. Note that the numbers start at 0. Easy to manipulate the data.

Declare an array

  1. A collection of data of the same type (which can be classes);

2) An array is an object;

3) Declare an array without creating an object;

4) Arrays can be declared in the following form:

Int [] I or int I []

Car[] c or Car c[]

* Only Car c in C++ []

[] c;

Create an array

  1. Int [] I = new int[2];

Car[] c = new Car[100];

3) The array has an initial value after creation.

The numeric type is 0, the Boolean type is false, and the reference type is NULL

Initialize the array

  1. Initialize, create, and separate declarations
int[] i;

i = new int[2];

i[0] = 0;

i[1] = 1;
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2) Initialize, create, and declare at the same time

Int [] I = {0, 1}; Car[] c = {new Car(),new Car()};Copy the code

Multidimensional arrays

  1. effective
      int[][] i1 = new int[2][3];

      int[][] i2 = new int[2][];

      i2[0] = new int[2],i2[1] = new int[3];
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*C++ int[][] =new int[][3]; effective

2) is invalid

     int[][] i1 = new int[][3];
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3) Array length ———— Array property length

int[] i = new int[5]; int len = i.length; //len = 5; Student[][] st = new Student[4][6]; len = st.length; //len = 4; len = st[0].length; //len = 6;Copy the code

Array copy

System.arrayCopy(Object src, int srcPos, Object dest, int destPos, int length);
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Copy an array to another array.