德.摩根De Morgan 和香农Shannon定理


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Java Base == & equals

  Tags:  Integer cache, == , equals This Blogger emphasizes that in actual development, developers should prioritize using .equals() to compare object values ​​rather than simply relying on == to compare references. Java's Integer cache mechanism provides memory optimization for Java programs with values ​​in the range of -128 to 127.However, values ​​outside this range will result in the creation of new objects, resulting in unexpected results in == comparisons.       public static void main(String[] args) {         Integer a = 228;         Integer b = 228;         System.out.println(a == b); // false         Integer x = 1;         Integer y = 1;         System.out.println(x == y); // true         Integer c = 228;         Integer d = 228;         System.out.println(System.identityHash...
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process.env in Node.js

process | Node.js http://nodejs.cn/api/process.html process is a global  object http://nodejs.cn/api/process.html#process_process_env demo in script： if (process.env.NODE_ENV === 'production') { module.exports = require('./prod.js') } else { module.exports = require('./dev.js') } input "node" line commend node > process.env  // show value On Windows: set test=testValue on OS X or Linux: export test=testValue In js file process.env.test= 'dev'; package.json： "scripts": { "start": "set test=dev && node app.js" } ------------------------ Windows environment variant cmd > set test-env   // exit set test-env=production set path=%path%;C:\web;C:\Tools set test-env= my computer -> property -> advance -> environment variant... ---------------------- Linux echo $test-env     //check value of test-env // set value of test-env export test-env=production # attach va...
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