A little morning light lights up the noisy world

There are many collection classes (the storage capacity can be changed, providing a storage model with variable storage space). Today we introduce one: ArrayList

ArrayList < E > <E> <E> : (resizable array implementation, followed by E is generic)

ArrayList < S t r i n g > <String> <String>, ArrayList < S t u d e n t > <Student> < student > (replace e with data type)

1: ArrayList construction method and addition method

Xiaoyedou first built a new project with the following structure:

First, we create a collection with the following code:
ArrayList<String> array = new ArrayList<String>();

package com.yedou_01;

import java.util.ArrayList;

public class ArrayListDe01 {
    public static void main(String[] args) {
        // public ArrayList(): create an empty collection object
        // New features after jdk7, the first way to create a collection (Annotated)
        // ArrayList<String> array = new ArrayList<>(); 
        ArrayList<String> array = new ArrayList<String>();
        // Output set
        System.out.println("array:" + array);
    }
}

Printout set, as follows:

The code after adding three elements is as follows: array Add ("night fighting Shrine");

package com.yedou_01;

import java.util.ArrayList;

public class ArrayListDe01 {
    public static void main(String[] args) {
        // public ArrayList(): create an empty collection object
        // ArrayList<String> array = new ArrayList<>();
        ArrayList<String> array = new ArrayList<String>();

        // public boolean add(E, e): appends the specified element to the end
        // Whether the printing is successful or not
        System.out.println(array.add("hello"));
        // Enter hello
        array.add("Night fighting Shrine");
        array.add("The road of the whole stack of night fighting");
        // Output set
        System.out.println("array:" + array);
    }
}

The results are as follows:

Insert the element at the specified position: array Add (1, "welcome to");

package com.yedou_01;

import java.util.ArrayList;

public class ArrayListDe01 {
    public static void main(String[] args) {
        // public ArrayList(): create an empty collection object
        // ArrayList<String> array = new ArrayList<>();
        ArrayList<String> array = new ArrayList<String>();

        // public boolean add(E, e): appends the specified element to the end
        // Whether the print input is successful
        System.out.println(array.add("hello"));
        // Enter hello
        array.add("Night fighting Shrine");
        array.add("The road of the whole stack of night fighting");
        // Insert element at specified position
        array.add(1,"Welcome to");
        // Output set
        System.out.println("array:" + array);
    }
}

However, this method has cross-border problems:
Exception in thread "main" java.lang.IndexOutOfBoundsException: Index: 4, Size: 3

array.add(4,"Welcome to");

If it is written as above, because there are only three elements and the Size is less than index, there is an error report that exceeds the boundary!

2: Common methods of ArrayList collection

First, we create a collection ArrayList, as shown below:

package com.yedou_01;

import java.util.ArrayList;

public class ArrayListDe02 {
    public static void main(String[] args) {
        ArrayList<String > array = new ArrayList<String >();
        array.add("Welcome to");
        array.add("Night bucket stack");
        array.add("Road of");
        System.out.println("array: " + array);
    }
}

array: [welcome to the whole stack of night fighting, the road to the world]

1. Delete element: system out. Println (array. Remove ("welcome");
2. According to index: system out. println(array.remove(0));
3. Modify element: system out. Println (array. Set (0, "Hello!");
4. Get element: system out. println(array.get(0));
5. Number of sets: system out. println(array.size());

The whole code is as follows:

package com.yedou_01;

import java.util.ArrayList;

public class ArrayListDe02 {
    public static void main(String[] args) {
        ArrayList<String > array = new ArrayList<String >();
        array.add("Welcome to");
        array.add("Night bucket stack");
        array.add("Road of");
        // Welcome to delete
        // Displays whether the deletion was successful
        System.out.println(array.remove("Welcome to"));
        // Delete by index
        System.out.println(array.remove(0));
        // Modify element value
        System.out.println(array.set(0,"Hello!"));
        // Returns the element at the specified index
        System.out.println(array.get(0));
        // Returns the number of sets
        System.out.println(array.size());
        // Print array
        System.out.println("array: " + array);
    }
}

3: ArrayList stores characters and traverses the collection

”I'm the man who wants to be the pirate king! "

We add the names and dreams of the straw hat party and print them out in a circle:

package com.yedou_02;

import java.util.ArrayList;

public class ArrayListTest01 {
    public static void main(String[] args) {
        // create object
        ArrayList<String> array = new ArrayList<String>();
        // Add object
        array.add("Monkey D Luffy: I'm the man who wants to be the pirate king");
        array.add("Sauron: I want to be the world's largest swordsman");
        array.add("Yamaguchi: I must find it All Blue!");
        array.add("Robin: I must find out the blank 100 year history");
        array.add("Nami: I want to find all the treasures in the world");
        array.add("Joba: why is my reward so low");
        array.add("Frankie: the Sonny I built is the most popular!");
        array.add("Brooke: my body, no, I'm just an old bone!");
        array.add("Usop: I'm sick of not being able to knock code!");
        array.add("I want to be a pirate king!");
        // Traversal object
        for(int i=0; i<array.size(); i++) {
            // Get element
            String s = array.get(i);
            // Print element
            System.out.println(s);
        }
    }
}

4: Store the straw hat pirate king object and traverse it

1: Create a straw hat class HatPirateGroup (set,get shortcut (alt + insert))

package com.yedou_02;
/*
Straw hat
 */
public class HatPirateGroup {
    private String name;
    private String sentence;

    // No reference
    public HatPirateGroup(){}

    // Have reference
    public HatPirateGroup(String name, String sentence){
        this.name = name;
        this.sentence = sentence;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSentence() {
        return sentence;
    }

    public void setSentence(String sentence) {
        this.sentence = sentence;
    }
}

2: Create a collection to store the members of the straw hat pirate and cycle through printing

package com.yedou_02;

import java.util.ArrayList;

public class ArrayListTest02 {
    public static void main(String[] args) {
        // Create collection object
        ArrayList<HatPirateGroup> array = new ArrayList<HatPirateGroup>();

        // Create a pirate object
        HatPirateGroup s1 = new HatPirateGroup("Monkey D Luffy:", "I'm the man who wants to be the pirate king");
        HatPirateGroup s2 = new HatPirateGroup("Sauron:","I want to be the world's largest swordsman");
        HatPirateGroup s3 = new HatPirateGroup("Yamaguchi:","I must find it All Blue!");

        // Add a pirate to the grass hat Pirate Group
        array.add(s1);
        array.add(s2);
        array.add(s3);

        // Traversal set
        for(int i=0; i<array.size(); i++){
            HatPirateGroup s = array.get(i);
            System.out.println(s.getName()+ s.getSentence());
        }

    }
}

5: Enter the straw hat pirate king object on the keyboard and traverse it

1: Create a straw hat class HatPirateGroup (set,get shortcut (alt + insert))

package com.yedou_02;
/*
Straw hat
 */
public class HatPirateGroup {
    private String name;
    private String sentence;

    // No reference
    public HatPirateGroup(){}

    // Have reference
    public HatPirateGroup(String name, String sentence){
        this.name = name;
        this.sentence = sentence;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSentence() {
        return sentence;
    }

    public void setSentence(String sentence) {
        this.sentence = sentence;
    }
}

2: Enter the pirate information on the keyboard and call the method to add it to the collection

package com.yedou_03;

import java.util.ArrayList;
import java.util.Scanner;

public class ArrayTest {
    public static void main(String[] args) {
        // Create collection object
        ArrayList<HatPirateGroup> array = new ArrayList<HatPirateGroup>();
        // Call method
        addPirate(array);
        addPirate(array);
        addPirate(array);

        // Traversal set
        for(int i=0; i<array.size(); i++){
            HatPirateGroup s = array.get(i);
            System.out.println(s.getName() + s.getSentence());
        }
    }
    public static void addPirate(ArrayList<HatPirateGroup> array){
        /*
        Methods: return value types and parameters
         */
        // Keyboard input data
        Scanner sc = new Scanner(System.in);

        System.out.println("Enter the name of the pirate:");
        String name = sc.nextLine();
        System.out.println("Please enter a sentence:");
        String sentence = sc.nextLine();

        // Create a pirate object
        HatPirateGroup s = new HatPirateGroup();
        s.setName(name);
        s.setSentence(sentence);

        // Add a student object to the collection
        array.add(s);
    }
}

• On this planet, you are very important. Please cherish your precious~~~ Night fighting Shrine