What is the usage of new in java

1. Use new to input data - instantiate the object and create memory

Example:

Scanner reader = new Scanner(System.in);

Scanner is A class, reader is a Scanner object created, new creates this instance and assigns variables to it.

Input basic type data: nextBoolean(), nextByte(), nextShort(), nextInt(), nextLong(), nextFloat(), nextDouble().

The usage is:

Scanner reader = new Scanner(System.in);//先创建对象

Then use

int x = reader.nextInt();

(Video tutorial recommendation: java video)

2. Allocate elements to the array

1. Declare the array

One-dimensional array: int a[] or int [] a; declare multiple at one time, int a[ ], b[] or int [] a, b;

Two-dimensional array: int a[][] or int [][] a; declare multiple at one time, int a[][], b [][] ;

Note: Java does not allow specifying the number of array elements within square brackets in the array declaration!

2. Allocate elements to the array

Array name = new array element type [number of elements];

For example: boy = new float [4]; (Prerequisite is that you have declared a float type boy variable! You can also declare and create it at the same time, for example: float boy = new float [4];)

Java allows you to use the value of an int type variable to specify the elements of an array. number. For example:

int size = 30;

double number = new double[size];

3. Use of length

For one-dimensional arrays, The value of "array name.length" is the number of elements in the array. For a two-dimensional array, the value of "array name.length" is the number of one-dimensional arrays it contains.

Recommended tutorial: Getting started with java development

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