Array Analysis in Java

Introduce the column first

This column is my own journey of learning Java, pure hand-knocked code, I followed the dark horse course to learn, and added some of my own understanding, and made
appropriate modifications to the code and notes. I hope it can be helpful to everyone, and at the same time, please supervise me, give suggestions on the code I wrote, and learn from each other.

array

In Java, arrays are a very importantdata structure. It is a set of elements of the same type that are stored sequentially in memory. Arrays provide an efficient way to store and access large amounts of data. Below I will explain arrays in Java in detail, and introduce some common operations and techniques.

Declare and initialize an array

In Java, there are various ways to declare and initialize arrays.

Method 1: Declare an array and allocate space: You can use the following syntax to declare an array and specify the length of the array.

dataType[] arrayName = new dataType[arrayLength];

example

To declare an integer array and allocate space you can use the following statement:

int[] numbers = new int[5];

Method 2: Declare an array and initialize elements: You can assign values ​​to the elements of the array at the same time when declaring the array.

dataType[] arrayName = {
    
    value1, value2, value3, ...};

example

To declare an array of strings and initialize elements, use the following statement:

String[] names = {
    
    "Alice", "Bob", "Charlie"};

Method 3: Assign values ​​one by one after declaring the array: You can declare an array first, and then assign values ​​to the elements of the array one by one.

dataType[] arrayName = new dataType[arrayLength];
arrayName[index] = value;

example

Declare an array of floats andone by one assignmentThe following statements can be used:

float[] grades = new float[3];
grades[0] = 90.5f;
grades[1] = 85.0f;
grades[2] = 92.3f;

Method 4: Use loops to assign values ​​to arrays: You can use loop structures to assign values ​​to elements of arrays.

dataType[] arrayName = new dataType[arrayLength];
for (int i = 0; i < arrayName.length; i++) {
    
    
    arrayName[i] = value;
}

example

Declare an array of integers and usecyclic assignmentThe following statements can be used:

int[] numbers = new int[5];
for (int i = 0; i < numbers.length; i++) {
    
    
    numbers[i] = i + 1;
}

basic operation

Accessing Array Elements: An index can be used to access an element in an array. Indexes start from 0, and elements in the array are accessed by enclosing the index in square brackets.

dataType element = arrayName[index];

example

Access the integer arrayfirst elementThe following statements can be used:

int firstElement = numbers[0];

Modify array elements: You can modify the elements in the array by index.

arrayName[index] = newValue;

example

Modify the integer arraythird elementThe following statements can be used:

numbers[2] = 100;

Get the length of the array: You can use the length property to get the length of the array.

int length = arrayName.length;

example

Get an array of integerslengthThe following statements can be used:

int arrayLength = numbers.length;

Traversing Arrays: You can use looping constructs to iterate over the elements in an array.

for (int i = 0; i < arrayName.length; i++) {
    
    
    // 执行操作
}

example

To iterate over an array of integers and print each element you can use the following statement:

for (int i = 0; i < numbers.length; i++) {
    
    
    System.out.println(numbers[i]);
}

Array Sorting: Arrays can be sorted using the static methods provided by the Arrays class.

Arrays.sort(arrayName);

example

rightinteger arrayconductascending orderSorting can use the following statements:

Arrays.sort(numbers);

Copying Arrays: Arrays can be copied using the static methods provided by the Arrays class.

dataType[] newArray = Arrays.copyOf(arrayName, length);

example

To copy an integer array you can use the following statement:

int[] newArray = Arrays.copyOf(numbers, numbers.length);