Inventory of common methods of list in Java Foundation (Part 1)

User 8211341 2021-04-16 18:09:59
inventory common methods list java


Hello everyone , I am a Java Initiate , Today, Xiao Bian will take you to study together Java Technology base !

One 、List Interface profile

List It's an ordered set 、 Repeatable sets . It's inheritance Collection Interface , stay List There are elements in a collection that can be duplicated , By index ( Subscript ) To access elements in the specified location .

Two 、List Common methods ——void add(int index,Obejct element) Method

1.void add(int index,Obejct element) The way is to put element The element is inserted in the specified position , The next element moves back one element .

2.void add(int index,Obejct element) Method example :

import java.util.ArrayList;
import java.util.List;
public class p6 {
public static void main(String[] args) {
// TODO Auto-generated method stub
List l = new ArrayList();
l.add("Java");
l.add(" The principle and application of database ");
l.add(" software test ");
l.add("Python actual combat ");
//l Gather all the elements
System.out.println("l Gather all the elements "+l);
// Inserts an element at the specified location
l.add(1," data structure ");
// After inserting elements l Gather all the elements
System.out.println(" After inserting elements l Gather all the elements "+l);
}
}

The result of the operation is :

3、 ... and 、List Common methods ——boolean addAll(int index,Collection c) Method

1.boolean addAll(int index,Collection c) The method is : Assemble c All the elements are inserted into List The set specifies the location .

2.boolean addAll(int index,Collection c) Method example :

import java.util.ArrayList;
public class p7 {
public static void main(String[] args) {
// TODO Auto-generated method stub
ArrayList<String> a1 = new ArrayList<String>();
a1.add("Java");
a1.add(" The principle and application of database ");
a1.add("C Language ");
System.out.println("a1 All elements of :"+a1);
ArrayList<String> a2 = new ArrayList<String>();
a2.add(" software test ");
a2.add("Python actual combat ");
a2.add("Java EE");
System.out.println("a2 All elements of :"+a2);
// stay a1 Insert... At specified location a2 All the elements
a1.addAll(2,a2);
System.out.println(" stay a1 Insert... At specified location a2 All the elements ,a1 All of the elements of are :"+a1);
}
}

The result of the operation is :

3、 ... and 、List Common methods ——Object get(int index) Method

1.Object get(int index) The method is to return List Sets the elements at the specified location .

2.Object get(int index) Method example

import java.util.ArrayList;
public class p8 {
public static void main(String[] args) {
// TODO Auto-generated method stub
ArrayList<String> a = new ArrayList<String>();
a.add(" software test ");
a.add("Java");
a.add("Python actual combat ");
a.add("PHP+MYSQL");
System.out.print(" The index value is 3 The elements of :"+a.get(3));
}
}

The result of the operation is :

Four 、List Common methods ——Object remove(int index) Method

1.Object remove(int index) The method is to delete the element at the specified location .

2.Object remove(int index) Method example

import java.util.ArrayList;
public class p8 {
public static void main(String[] args) {
// TODO Auto-generated method stub
ArrayList<String> a = new ArrayList<String>();
a.add(" software test ");
a.add("Java");
a.add("Python actual combat ");
a.add("PHP+MYSQL");
System.out.println(" The delete index value is 3 The elements of :"+a.remove(3));
System.out.println("a All the elements in :"+a);
}
}

The result of the operation is :

5、 ... and 、List Common methods ——int indexOf(Object o) Method

1.int indexOf(Object o) The method is to return the object o stay List Index of where the collection appears , If no object appears o, Then return to -1.

2. The code is as follows :

import java.util.ArrayList;
public class p9 {
public static void main(String[] args) {
// TODO Auto-generated method stub
ArrayList<String> a = new ArrayList<String>();
a.add(" software test ");
a.add("Java");
a.add("Python actual combat ");
a.add("PHP+MYSQL");
System.out.println("a All of the elements in are :"+a);
int num=a.indexOf("Python actual combat ");
System.out.println(" First appearance \"Python actual combat \" The index value of is :"+num);
num=a.indexOf(" data structure ");
System.out.println(" First appearance \" data structure \" The index value of is :"+num);
}
}

The result of the operation is :

6、 ... and 、 summary

This paper mainly introduces List Interface profile ,List Common methods .

List It's an ordered set 、 Repeatable sets .List Common methods are void add(int index,Obejct element) Method 、boolean addAll(int index,Collection c) Method 、Object get(int index) Method 、int indexOf(Object o) Method , This paper introduces what their methods are used for , Use examples to help understand .

I am a Java Initiate , I hope you can learn from this article , It helps you ! Welcome to WeChat , If you have any problems, you can help us solve them at any time , It's good to make a friend ~

This article is from WeChat official account. - Java Advanced learning communication (java_xianghong) , author :Java Initiate

The source and reprint of the original text are detailed in the text , If there is any infringement , Please contact the [email protected] Delete .

Original publication time : 2021-04-12

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