Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/
gm

Test String

Substitution

Processing...

Code Generator

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "(\\/\\/.*| ?\\/\\*[^]*?\\*\\/)(,?)$"; final String string = "/**\n" + " * \n" + " * \n" + " * a multi-line example just for fun\n" + " */\n\n" + "{\n" + " \"compilerOptions\": {\n" + " /* Visit https://aka.ms/tsconfig.json to read more about this file */\n\n" + " /* Basic Options */\n" + " // \"incremental\": true, /* Enable incremental compilation */\n" + " \"target\": \"ES6\" /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */,\n" + " \"module\": \"commonjs\" /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */,\n" + " \"lib\": [\"dom\", \"es6\"] /* Specify library files to be included in the compilation. */,\n" + " \"allowJs\": true /* Allow javascript files to be compiled. */,\n" + " // \"checkJs\": true, /* Report errors in .js files. */\n" + " // \"jsx\": \"preserve\", /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */\n" + " \"declaration\": true /* Generates corresponding '.d.ts' file. */,\n" + " \"declarationMap\": true /* Generates a sourcemap for each corresponding '.d.ts' file. */,\n" + " // \"sourceMap\": true, /* Generates corresponding '.map' file. */\n" + " // \"outFile\": \"./\", /* Concatenate and emit output to single file. */\n" + " // \"outDir\": \"./dist\" /* Redirect output structure to the directory. */,\n" + " // \"rootDir\": \"./\", /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */\n" + " // \"composite\": true, /* Enable project compilation */\n" + " // \"tsBuildInfoFile\": \"./\", /* Specify file to store incremental compilation information */\n" + " // \"removeComments\": true, /* Do not emit comments to output. */\n" + " // \"noEmit\": true, /* Do not emit outputs. */\n" + " // \"importHelpers\": true, /* Import emit helpers from 'tslib'. */\n" + " // \"downlevelIteration\": true, /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */\n" + " // \"isolatedModules\": true, /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */\n\n" + " /* Strict Type-Checking Options */\n" + " \"strict\": true /* Enable all strict type-checking options. */,\n" + " // \"noImplicitAny\": true, /* Raise error on expressions and declarations with an implied 'any' type. */\n" + " // \"strictNullChecks\": true, /* Enable strict null checks. */\n" + " // \"strictFunctionTypes\": true, /* Enable strict checking of function types. */\n" + " // \"strictBindCallApply\": true, /* Enable strict 'bind', 'call', and 'apply' methods on functions. */\n" + " // \"strictPropertyInitialization\": true, /* Enable strict checking of property initialization in classes. */\n" + " // \"noImplicitThis\": true, /* Raise error on 'this' expressions with an implied 'any' type. */\n" + " // \"alwaysStrict\": true, /* Parse in strict mode and emit \"use strict\" for each source file. */\n\n" + " /* Additional Checks */\n" + " // \"noUnusedLocals\": true, /* Report errors on unused locals. */\n" + " // \"noUnusedParameters\": true, /* Report errors on unused parameters. */\n" + " // \"noImplicitReturns\": true, /* Report error when not all code paths in function return a value. */\n" + " // \"noFallthroughCasesInSwitch\": true, /* Report errors for fallthrough cases in switch statement. */\n\n" + " /* Module Resolution Options */\n" + " // \"moduleResolution\": \"node\", /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */\n" + " \"baseUrl\": \"./\" /* Base directory to resolve non-absolute module names. */,\n" + " \"paths\": {\n" + " /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */\n" + " /* TODO: Fix alias resolution with cypress */\n" + " \"@lib\": [\"cypress/lib\"],\n" + " \"@lib/*\": [\"cypress/lib/*\"],\n" + " \"@log/browser\": [\"cypress/support/customCommands/browserLog\"],\n" + " \"@log/node\": [\"cypress/lib/nodeLog\"],\n" + " \"@tasks\": [\"cypress/plugins/tasks\"],\n" + " \"@tasks/*\": [\"cypress/plugins/tasks/*\"]\n" + " },\n" + " // \"rootDirs\": [], /* List of root folders whose combined content represents the structure of the project at runtime. */\n" + " // \"typeRoots\": [], /* List of folders to include type definitions from. */\n" + " \"types\": [\"node\", \"cypress\", \"./types\"] /* Type declaration files to be included in compilation. */,\n" + " // \"allowSyntheticDefaultImports\": true, /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */\n" + " \"esModuleInterop\": true /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */,\n" + " // \"preserveSymlinks\": true, /* Do not resolve the real path of symlinks. */\n" + " // \"allowUmdGlobalAccess\": true, /* Allow accessing UMD globals from modules. */\n\n" + " /* Source Map Options */\n" + " // \"sourceRoot\": \"\", /* Specify the location where debugger should locate TypeScript files instead of source locations. */\n" + " // \"mapRoot\": \"\", /* Specify the location where debugger should locate map files instead of generated locations. */\n" + " // \"inlineSourceMap\": true, /* Emit a single file with source maps instead of having a separate file. */\n" + " // \"inlineSources\": true, /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */\n\n" + " /* Experimental Options */\n" + " // \"experimentalDecorators\": true, /* Enables experimental support for ES7 decorators. */\n" + " // \"emitDecoratorMetadata\": true, /* Enables experimental support for emitting type metadata for decorators. */\n\n" + " /* Advanced Options */\n" + " \"skipLibCheck\": true /* Skip type checking of declaration files. */,\n" + " \"forceConsistentCasingInFileNames\": true /* Disallow inconsistently-cased references to the same file. */,\n" + " \"resolveJsonModule\": true,\n" + " \"noEmit\": true // We should not be using transpiled code at all. We only need to run tsc to ensure type checking!\n" + " },\n" + " \"include\": [\"cypress/**/*.ts\", \"npm-scripts/**/*.ts\", \"ops/**/*.ts\", \"cypress.json\", \"cypressRunner.ts\", \"customBootstrapCommand.ts\"],\n" + " \"exclude\": [\"**/*.ignore.*\", \"**/*ignore*/*\", \"build\", \"dist\", \"node_modules\"]\n" + "}\n"; final String subst = "$2"; final Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE); final Matcher matcher = pattern.matcher(string); // The substituted value will be contained in the result variable final String result = matcher.replaceAll(subst); System.out.println("Substitution result: " + result); } }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html