A complete set of in-depth exploration of Java arrays - basic knowledge stage 2, definition syntax of arrays
Table of contents
The importance of array learning
How to understand the random access of arrays
General article link:https://laoshifu.blog.csdn.net/article/details/134906408
The importance of array learning
Arrays are one of the data structures that we must master, and they will be of great help to us in the future.
- Improve program efficiency: Array is an efficient data structure that can quickly access and modify data. In actual production and life, arrays are widely used in various scenarios that require efficient data processing, such as image processing, scientific computing, financial analysis, etc. By learning arrays, students can process data more efficiently and improve program execution efficiency.
- Enhance programming abilities: Arrays are one of the commonly used data structures in programming. Mastering the use of arrays is very important for students to improve their programming abilities. In the actual programming process, the use of arrays is very common. Mastering the use of arrays can help students become more proficient in programming and improve programming efficiency and code quality.
- Cultivate logical thinking: Array is an abstract data structure. By learning arrays, students can develop their logical thinking abilities. In actual problem solving, many problems can be transformed into array processing problems. By learning arrays, students can think about problems more clearly and come up with effective solutions.
Learning arrays can be a somewhat difficult task for students, but if you keep studying, you can master it. Here are some words of encouragement for students learning about arrays:
- Arrays are the basis of programming, and mastering the use of arrays is very important to becoming a good programmer.
- Learning arrays can be difficult, but if you stick with it, you'll be able to master it.
- By learning arrays, you can process data more efficiently, improve program execution efficiency, and show your programming abilities.
- Arrays are widely used. Mastering the use of arrays can make you better in your future study and work.
- Believe in yourself, you will be able to master the use of arrays and become an excellent programmer!
Array definition syntax
In Java, an array is a special type of variable used to store an ordered collection of the same data type. The definition syntax of an array consists of data type, array name and array size.
First, you need to specify the data type of the array, which can be any basic data type in Java (such as int, double, char, etc.) or a reference data type (such as a custom class, interface, etc.). The data type is followed by a pair of square brackets [] to indicate that it is an array.
Next, you need to choose an appropriate name for the array, the array name. Array names should be descriptive and clearly express the purpose and meaning of the array.
Finally, create the array instance using the new keyword and the array size. The array size is an integer that represents the number of elements in the array. You can choose to initialize the array elements directly when defining the array, or assign values one by one later in the program.
To sum up, the definition syntax of an array can be expressed in the following format:
Data type [] array name = new data type [array size];
Array definition example
In Java, the definition syntax of an array includes data type, array name and array size. The following is an example of defining an array of integers:
int[] array = new int[5]; //Define an integer array of length 5
In this example, int[] represents the data type of the integer array, array is the name of the array, and new int[5] creates a new integer array instance of length 5.
You can also initialize the array elements while defining the array, as follows:
int[] array = {1, 2, 3, 4, 5}; // Define and initialize an integer array
In this example, the numbers inside the curly brackets are the elements of the array, and they will be automatically assigned to various positions in the array.
Interpretation of [I@15db9742
[I@15db9742 is the default toString output for array objects in Java. Interpretation is as follows:
[Indicates that the currently accessed array is a one-dimensional array.
I indicates that the elements currently stored in the array are of type int.
@ is an ordinary delimiter.
15db9742 is the hexadecimal representation of the hash code value of this array object in memory. This hash code is calculated using the hashCode method and is used to uniquely identify this array object in memory.
Therefore, [I@15db9742 can be interpreted as: a one-dimensional array containing elements of type int with a hash code value of 15db9742.
It should be noted that this output is not the content of the array, but the identification information of the array object. To view the contents of an array, you can use a loop to loop through the array and print each element, or use the Arrays.toString(array) method to convert the array contents to a string output.
View arrays through Debug
When using debug, we can see the contents of the corresponding array.
length definition
All initial values of the length definition are 0, and the subscripts are calculated from 0.
assignment definition
The specific assignment value definitions are arranged according to the content of the assigned value, and the subscripts are calculated from 0.
Summary of array properties
The characteristics of arrays can be summarized as follows:
Orderliness: The elements in the array are arranged in a certain order, and each element has a fixed index position.
Data type consistency: Only elements of the same data type can be stored in the array, and each element occupies the same memory space.
Fixed size: The size of the array needs to be specified when it is created. Once created, the size of the array is fixed.
Random access: Through indexing, you can directly access any element in the array, and the access time complexity is O(1).
Memory continuity: The elements in the array are stored continuously in memory, which helps improve space utilization and access efficiency.
Static structure: An array is a static data structure whose size and content cannot be dynamically adjusted at runtime.
How to understand the random access of arrays
The random access of an array means that any element in the array can be directly accessed through the index, without the need to access the elements one by one in the order in which they are physically stored in the array. Specifically, if we know the index position of an element, we can directly calculate the address of the element in memory and directly access the element through that address. Therefore, no matter how many elements there are in the array, as long as we know the index position of the element, we can access the element in constant time. This property makes arrays very efficient when working with large amounts of data, because we can quickly access and modify elements at any location without traversing the entire array.
It should be noted that the random access of arrays is based on the continuous storage of array elements in memory. If the array is not stored contiguously in memory, or if there are other factors that prevent the memory address of the elements from being directly calculated, the random access of the array may be affected.