Shulou(Shulou.com)06/02 Report--

This article mainly introduces the example analysis of Java object-oriented array, which is very detailed and has certain reference value. Friends who are interested must finish it!

An array of Java face objects

1. One-dimensional array

1. Description of the array: a combination of the same type of data.

Description: the ① array is a reference data type, and the elements of the array can be basic data types or reference data types.

two。 Declaration and initialization of one-dimensional array

① dynamic initialization: array declaration and initialization are performed separately

Int [] numbers = new int [5]

② static initialization: array declaration and initialization occur at the same time

Int [] numbers = new int [] {1pm 2pm 3pm 4}

Int [] numbers = {1pm 2pm 3pm 4}

Note: the length of the array is immutable once the array is created, either dynamically or statically.

3. Reference to one-dimensional array elements: subscript (index value)-subscript is the length from 0 to the array-1

Int [] numbers = new int [2]

Numbers [0] = 1; / / assignment

System.out.println (numbers [0]); / / get the value of the element

4. Properties of the array: length- represents the length of the array

Int [] numbers = new int [2]

Int l = numbers.length

5. Traversal of one-dimensional array

Int [] numbers = new int [2]

For (int I = 0; I < numbers.length; iTunes +) {

System.out.println (numbers [I])

}

6. Default initialization values for one-dimensional array elements: the same as the default values for basic and reference data types.

7. Memory structure of one-dimensional array

Painted by ps:Excel, average level, make do with it.

two。 Two-dimensional array

1. How to understand two-dimensional array? The elements in a two-dimensional array are one-dimensional arrays. (elements in an array or an array)

Description: elements of a two-dimensional array are reference data types

two。 Declaration and initialization of two-dimensional array

/ / dynamic initialization

String [] [] persons = new String [2] [3]

String [] persons = new String [2] []

Persons [0] = new String [2]

Persons [1] = new String [5]

/ / static initialization

String [] [] persons = new String [] [] {{"a", "110"}, {" b "," 120"}}

String [] [] persons = {{"a", "110"}, {" b "," 120th "}}

3. How to reference a two-dimensional array element: get the element at a location in the array by using the subscript

String [] [] persons = {{"a", "110"}, {" b "," 120th "}}

System.out.println (persons [0] [0])

4. Property of 2D array: length

String [] [] persons = {{"a", "110"}, {" b "," 120th "}}

Length of persons.length; / / two-dimensional array

Persons [0] .length; / / the length of the element at position 0 in the two-dimensional array

5. Traverse two-dimensional array elements:

String [] [] persons = {{"a", "110"}, {" b "," 120th "}}

For (int I = 0; I < persons.length; iTunes +) {

For (int j = 0; j < persons [I] .length; jacks +) {

System.out.println (persons [I] [j])

}

}

6. Default initialization values for two-dimensional array elements:

The default value for the elements of the ① 2D array is null

The default values and basic data types of the elements of the ② two-dimensional array are the same as the reference data types.

7. Memory structure of two-dimensional array

3.Arrays utility class

Because under the lang package, there is no need for the guide package to call the

Int [] numbers = {12pm 38pm 1je 2je 3je 4je 5je 6}

Int [] numbers2 = {12pm 38pm 1je 2je 3je 4je 5}

/ / determine whether two arrays are equal (the value and number of elements)

Boolean equals = Arrays.equals (numbers, numbers2)

System.out.println (equals)

/ / toString (): outputs the elements in the array

String str = Arrays.toString (numbers)

System.out.println (str)

/ / fill (int [] njinint val): change the value of the array element to val

Arrays.fill (numbers, 100)

Str = Arrays.toString (numbers)

System.out.println (str)

/ / sort (int [] numbers)

Arrays.sort (numbers2)

System.out.println (Arrays.toString (numbers2))

/ / dichotomy search: premises must be sorted. If you can't find a return-1

Int index = Arrays.binarySearch (numbers2, 1)

System.out.println (index)

4. Common anomalies

Int [] numbers = new int [2]

/ *

*

* ArrayIndexOutOfBoundsException

, /

/ / numbers [2] = 5; the subscript is out of bounds

/ / numbers [- 1] = 10

/ / int [] [] n = new int [2] []

/ / n [2] = new int [10]

/ *

* NullPointerException

, /

String [] str = {"aa", "bb"}

/ / String string = str [0] .toUpperCase ()

/ / System.out.println (string)

Str = new String [2]

/ / System.out.println (str [0] .toString ())

5. Deformable parameter

* deformed parameters:

*

* format: public void add (int... Numbers {}

*

* description:

* 1. Deformable parameters of the same type and arrays of the same type are not overloaded (the type is the same as the number)

* 2. Deformable parameters can only be placed on the last one in the formal parameter list.

* 3. There can be only one deformable parameter in a method

* 4. The number of deformable parameters can be 0 or 1 or more

The above is all the content of the article "sample Analysis of Java object-oriented Array". Thank you for reading! Hope to share the content to help you, more related knowledge, welcome to follow the industry information channel!

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.