About collection framework

Overview of collection framework

The collection framework can be understood as an array

java officially encapsulates many classes based on arrays and different data structures. These classes are collectively referred to as collection framework.

1.List table

1.1 characteristics of list table

You can precisely control the insertion position of each element in the list

Users can access elements from locations in the list and search for elements in the list

Common methods of addition, deletion, modification and query

It can be simply understood as similar to the use of arrays

1.2 # ArrayList create array

(1) Call class first

import java.util.ArrayList;
import java.util.List;

(2) Create ArrayList

                1. Default capacity ArrayList

public static void main(String[] args) {
        List  list =  new ArrayList();

}

2. Customize the initial capacity List

public static void main(String[] args) {
        List  list =  new ArrayList(6);

}

1.3 adding data to ArrayList

(1) Variable name add("data content")

package com.Text;

import java.util.ArrayList;
import java.util.List;

public class java001 {
    public static void main(String[] args) {
        List  list =  new ArrayList();
        list.add("java01");
}

(2) Variable name Add (subscript position to add data, "data content")

package com.Text;

import java.util.ArrayList;
import java.util.List;

public class java001 {
    public static void main(String[] args) {
        List  list =  new ArrayList();
        list.add("java01");
        list.add(3,"java002");
}

1.4 # ArrayList delete data (data is automatically shifted forward)

(1) Delete the "data" # variable name in the list remove("data content")

package com.Text;

import java.util.ArrayList;
import java.util.List;

public class java001 {
    public static void main(String[] args) {
        List  list =  new ArrayList();
        list.remove("java01");
    
}

(2) Deletes the subscript content # variable name at a specific location Remove (subscript position)

​
package com.Text;

import java.util.ArrayList;
import java.util.List;

public class java001 {
    public static void main(String[] args) {
        List  list =  new ArrayList();
        list.remove(2);
    
}

(3) After deleting the content, the return value is the deletion result

​
package com.Text;

import java.util.ArrayList;
import java.util.List;

public class java001 {
    public static void main(String[] args) {
        List  list =  new ArrayList();
        boolean remove = list.remove("java01");
    
}

​

1.5 # ArrayList modify data

(1) Delete the file first and add # variable name in Set (subscript position, "modified content")

​
package com.Text;

import java.util.ArrayList;
import java.util.List;

public class java001 {
    public static void main(String[] args) {
        List  list =  new ArrayList();
        list.set(2."java02");
    
}

​

1.6. ArrayList query data

(1) Query all sets #int variable name = variable name size();

package com.Text;

import java.util.ArrayList;
import java.util.List;

public class java001 {
    public static void main(String[] args) {
        List  list =  new ArrayList();
        list.add("java01");
        int size = list.size()
}

(2) get method query subscript #Object variable name = variable name get (subscript position)

package com.Text;

import java.util.ArrayList;
import java.util.List;

public class java001 {
    public static void main(String[] args) {
        List  list =  new ArrayList();
        list.add("java01");
        Object a = list.get(1)
}

(3) The first and last positions that appear do not return - 1

Subscript position where the first content appears: int variable name = variable name indexOf("content");
The subscript position of the last content: int variable name = variable name lastIndexOf("content");

(4) For loop and for each

package com.Text;

import java.util.ArrayList;
import java.util.List;

public class java001 {
    public static void main(String[] args) {
        List  list =  new ArrayList();
        list.add("java01");
        

        for (int i = 0; i < list.size(); i++) {
            Object a1 = list.get(i);
            System.out.println(a1);
        }

        for (Object a2 :list){
            System.out.println(a2);
        }
}

2.LinkedList

2.1 # differences between LinkedList and ArrayList

ArrayList # the underlying data structure is array
The underlying data structure of Linkedlist is linked list


2.2 creation of LinkedList

Import package: import Java util. LinkedList;

LinkedList} variable name = new LinkedList();

package com.Text;

import java.util.LinkedList;

public class java002 {
    public static void main(String[] args) {
        LinkedList  linkedList =  new LinkedList();
        
}

2.3 adding Linkedlis

(1) variable name add("data content")

package com.Text;

import java.util.LinkedList;

public class java002 {
    public static void main(String[] args) {
        LinkedList  linkedList =  new LinkedList();
             linkedList.add("Zhang San");
        
}

(2) Variable name Add (subscript position to add data, "data content")

package com.Text;

import java.util.LinkedList;

public class java002 {
    public static void main(String[] args) {
        LinkedList  linkedList =  new LinkedList();
             linkedList.add(2,"Zhang San");
        
}

2.4 deletion of Linkedlis

(1) delete the "data" # variable name remove("data content")

package com.Text;

import java.util.LinkedList;

public class java002 {
    public static void main(String[] args) {
        LinkedList  linkedList =  new LinkedList();
             linkedList.add(2,"Zhang San");
             linkedList.remove("Zhang San");
        
}

(2) Deletes the subscript content # variable name at a specific location Remove (subscript position)

package com.Text;

import java.util.LinkedList;

public class java002 {
    public static void main(String[] args) {
        LinkedList  linkedList =  new LinkedList();
             linkedList.add(2,"Zhang San");
             linkedList.remove(2);
        
}

2.5 modification of Linkedlis

(1) Delete the file first and add # variable name in Set (subscript position, "modified content")

package com.Text;

import java.util.LinkedList;

public class java002 {
    public static void main(String[] args) {
        LinkedList  linkedList =  new LinkedList();
             linkedList.add(2,"Zhang San");
             linkedList.set(2,"Li Si");
        
}

2.6. Linkedlis query

(1) Query all linked lists #int variable name = variable name size();

package com.Text;

import java.util.LinkedList;

public class java002 {
    public static void main(String[] args) {
        LinkedList  linkedList =  new LinkedList();
             linkedList.add(2,"Zhang San");
               int size = linkedList.size();
        
}

(2) get method query subscript #Object variable name = variable name get (subscript position)

package com.Text;

import java.util.LinkedList;

public class java002 {
    public static void main(String[] args) {
        LinkedList  linkedList =  new LinkedList();
             linkedList.add(2,"Zhang San");
               int size = linkedList.size();
        
}

Tags: Java

Posted by animuson on Sat, 16 Apr 2022 11:40:05 +0930