Shell set command application

catalogue Introduction to set command Using the set command 1. Execute the set command without options 2. Basic grammar 3. Introduction to options -o +o -e or -o errexit -n or -o noexec -u or -o unset -x or -o xtrace -o pipefail example Introduction to set command The set command is a command that beginners in the shell seldom t ...

Posted by ns1025 on Sun, 26 Dec 2021 08:40:48 +0100

Summary of common collection classes in Java

Diagram This figure is inaccurate for the underlying implementation method of some implementation classes, which has changed in the new version of JVM, such as HashMap, but the inheritance and implementation relationship has not changed. Solid white arrows are inheritance and blue dashed arrows are implementation. Map HashMap Before ja ...

Posted by mwd2005 on Mon, 20 Dec 2021 16:51:52 +0100

JAVA collection learning notes

Advantages and disadvantages of arrays and collections Advantages of arraysDisadvantages of arraysSimple definition and quick accessImmutable length after initializationAfter definition, the type is singleThe methods provided are limited, inconvenient to insert, delete and other operations, and the efficiency is not highThere is no method to g ...

Posted by Lodius2000 on Sat, 11 Dec 2021 07:16:44 +0100

JAVA - API -Map HashMap set HashSet

Map interface summary Java.util interface map < K, V > Type parameter: K - indicates the key maintained by this mapping; V - indicates the corresponding value maintained by this mapping It is also called hash table and hash table. It is often used for data of key value pair structure. The key cannot be repeated, and the value can be ...

Posted by zoozle on Sat, 20 Nov 2021 00:00:32 +0100

Use of Java collections

Overview of the collection framework Collection and array are structures that store multiple data, which are referred to as Java containers for short. Storage at this time mainly refers to memory level storage and does not involve persistent storage (such as. txt,. jpg, database, etc.) The characteristics of arrays in storing multip ...

Posted by stitchmedia on Sun, 17 Oct 2021 19:56:56 +0200

ArrayList source code analysis

10.15 analysis of ArrayList collection source code The code used for the test is as follows public static void main(String[] args) { List list = new ArrayList(); for (int i = 0; i < 10; i++) { list.add(i); } list.add(20); list.add(30); list.add(40); } First, create an ...

Posted by Judas on Sat, 16 Oct 2021 10:35:35 +0200

Map interface overview

1 Map interface Map and Collection have no inheritance relationship The Map collection stores data in the form of key and value: key value pairs Both key and value are reference data types. Both key and value are memory addresses of storage objects. Key plays a leading role, and value is an accessory of key. Common methods in Map interf ...

Posted by sunil.23413 on Mon, 06 Sep 2021 05:14:54 +0200