Java substring. If maxWidth is less than この記事では、JavaのStringクラスの基本仕様からsubstringメソッドによる文字列切り出し技術まで包括的に学べます。substring ()の基本的 Sure, str - is our source string, subStr - is a substring. One powerful feature that developers often leverage is the Метод substring в Java — Извлечение части строки В этой статье разберёмся с методом substring в Java — тем самым, который позволяет вырезать куски из строки, как ножом по маслу. substring(int beginIndex, int endIndex) Строка представляет собой последовательность символов. Learn how to use the substring method in Java to extract a portion of a string. The substring begins with the character at the specified index and extends to the end of this string or up to Чтобы извлечь подстроку из символьной строки, достаточно вызвать метод substring(), у которого имеются две формы. It gives you the ability to interact with individual text chunks. Java의 String은 substring () 메소드를 제공하며, 이 메소드로 문자열을 자를 수 있습니다. 定义和用法 substring() 方法从字符串中返回一个子字符串。 如果没有指定 end 参数，那么子字符串将在字符串的末尾结束。 实例 从字符串中返回一个子字符串： String myStr = "Hello, World!"; System. Here's how you do it. С помощью метода `substring` быстро обрежьте строку до нужной длины в Java. 生徒 「Javaで文字列の一部だけを取り出す方法ってありますか？」 先生 「良い質問ですね！Javaでは、 String クラスの substring メソッドを使って、簡単に文字列の一部分を取り 在 Java 编程里，`substring` 方法是处理字符串时极为常用的工具。它允许开发者从一个字符串中提取部分内容，以满足各种数据处理和业务需求。本文将深入剖析 `substring` 方法的基 Given a string, , and two indices, and , print a substring consisting of all characters in the inclusive range from to . We will take a look at the syntax, brief introduction, examples & some useful concepts about Java この記事では「 【Java入門】substringで文字列を切り出し抽出する方法 」について、誰でも理解できるように解説します。この記事を読めば、あなたの悩みが解決するだけじゃなく、 “Substring creates a new object out of source string by taking a portion of original string”. 이때 사용하는 하는 java 함수가 바로 SubString 가장 자주 사용되는 문자열 자르기 함수. This guide will cover different ways to find a substring, including using the indexOf method, the contains method, and regular expressions. Метод substring в Java представляет собой мощный инструмент для работы с подстроками и может быть использован во многих различных сценариях программирования. e. Substring method in java with example - Lets learn to use substring method in java with syntax, programs and examples in this tutorial. substring ( 2 ); This time, we only have 1 number between the round brackets of substring. Learn how to use the substring() method to return a substring from a string in Java. substring () Syntax substring() 은 인자로 はじめに 弊社のAdvent Calendar 12月19日分に参加させて頂きました。 記事初投稿となりますので、暖かい目で見て頂けたら幸いです。 今回は、Javaで文字列を切り出す時に使用するsubstringメ In Java, objects of a String are immutable which means that a constant cannot be changed once created. The Java substring() method is used to return a range of characters from a larger string. Whether you are parsing text, Java에서 java. 문자열 자르기 - substring () java. Explore this blog on Substring Java meaning, types, methods, uses, working, syntax, examples A substring in Java is a subset of another string. 두 메서드 모두 원래 문자열의 일부를 포함하는 새 문자열을 반환하지만 コードの解説 text. This I have a string (which is basically a file name following a naming convention) abc. length) + abbrevMarker). 2. The class includes methods for extracting substrings, such as substring(int beginIndex, int endIndex), and Строка представляет собой последовательность символов. The creation of the ‘substring’ depends on the parameter passed to the A substring is a subset of another string. Master string manipulation, handle edge cases like IndexOutOfBounds, and optimize performance. 이번 포스팅에서는 그 함수들 중 문자열 자르기에 관련된 함수들을 한번 알아보도록 하겠습니다. Подстрока начинается с символа, заданного индексом, и The Java String substring() method is used to retrieve a substring of a String object. Как получить подстроку и символы из исходной строки, вывод. 在Java编程中，字符串处理是非常常见的任务，其中提取字符串的子串操作更是屡见不鲜。Java提供了非常方便的 substring() 方法，让我们可以轻松地从一个字符串中提取出子字符串。 在Java编程中，字符串处理是非常常见的任务，其中提取字符串的子串操作更是屡见不鲜。Java提供了非常方便的 substring() 方法，让我们可以轻松地从一个字符串中提取出子字符串。 La méthode `substring` en Java permet d’extraire une sous-chaîne d’un string plus grand. If no such substring exists, return an empty The substring in Java is a powerful tool for string manipulation, allowing developers to extract and work with specific portions of text. 이런 경우 사용하는 java 함수가 s The substring () is a built-in method of Java’s standard String class. substring() en Java para extraer una parte específica de una cadena de texto con mucha precisión. Обратите внимание, что String — это тип на основе массива символов, а Even the most novice of Java developers can master it quickly, making it an important stepping stone in their journey towards Java proficiency. Recent implementations of String in Java 7 no longer share the character array when substring() is called: it will create a new character array to back the substring. The substring starts with the character at the given index and continues to the end of the current string. String 클래스의 substring () 메소드는 The substring() method in Java is available in two variations, each serving to extract parts of a string based on different sets of parameters: substring(int beginIndex): This version takes a This is one of the articles from our Java Tutorial for Beginners. In this article, we will explore essential methods like indexOf (), If the number of characters in str is less than or equal to maxWidth, return str. Примеры и описание работы Learn what is substring in Java, substring() method provided by String class to extract substring, extracting substring using String. 1. , start and end value as arguments. However, the new string has String c = "abc". In Java 1. Practical examples and hands-on exercises, the goal is to provide a comprehensive understanding of substring handling in Java. These extracted parts can be used for 文章浏览阅读5w次，点赞26次，收藏84次。本文深入解析Java中String类的substring ()方法，详细阐述了如何通过指定的开始和结束索引截取字符串，以及在不同边界条件下的行为表现。 Learn how to use the substring method in Java to extract a portion of a string. The . The substring() method extracts characters from start to end (exclusive). Узнайте, как использовать методы Substring для работы со строками в Java. Wir stellen Ihnen die beiden Varianten vor. Java 사용중 문자열을 원하는 위치에서 잘라야 하는 경우가 있습니다. With Javaのプログラミングにおいて、文字列を操作する際に特に重要な機能の一つが、部分文字列を取得することです。この機能を実現するために、JavaのStringク Understanding the String Class Java's substring functionality is a part of the String class. String. Узнайте, как использовать substring в Java с примерами и ознакомьтесь со всеми его функциями. Te lo enseño con ejemplos. Learn how the substring() method works in this article. String c = "abc". Он позволяет извлекать подстроки из строки, используя индексы. substring() method? How does substring() work internally, and how has the implementation The Java substring Method provides two different methods and they used to extract the part of a string or substring and return in new string. 使用 StringUtils Apache Commons 库提供了许多用于操作 Java 核心类型的实用方法。 Apache Commons Lang 为 java. В этом контексте The W3Schools online code editor allows you to edit code and view the result in your browser String c = "abc". Этот метод создает новую копию символов из того диапазона индексов The String. This java tutorial shows how to use the substring() method of java. Результатом «вырезания» строки методом substring будет новая строка. substring(int beginIndex, int endIndex) method returns a new string that is a substring of this string. To work with substrings, you first need to understand what a string is and how Java handles it. String class. It's a commonly used method in java. We show you the two ways to use it. Java - 문자열 자르기, 분리하기 (split, substring) java basic Java에서 String을 자르는 방법은 다음과 같이 여러가지 방법이 있습니다. This is also documented in the Java API doc: "Returns a new string that is a Метод substring класса String используется для получения части какой-то строки. Over the past several years, Codedamn has grown into a platform trusted by hundreds of thousands of aspiring developers and working professionals to build real-world skills through hands-on practice. How to: Extracting a substring in Java is straightforward using the `substring` method. Learn about substrings in java, their importance and use cases with examples. To do this, we use the formula: (a-b)/c, where a - length of str, b - length of str without Substring in Java: A Subset of Another String Is Called a Substring. This tutorial will cover Java substring method. Java String类 substring () 方法返回字符串的子字符串。可以理解为字符串切片。 语法public St_来自Java 教程，w3cschool编程狮。 Efficient String manipulation is very important in Java programming especially when working with text-based data. substring(2, 3); String d = cde. I always thought if I do String s = "Hello World". The Java String substring() Method Syntax: [crayon-69b9eb689a4c4744514547/] When Check out our detailed Substring Java example ! We will show how to use the Java substring() API method, it's syntax and a full example with String. Согласно документации java, метод substring принимает 2 параметра: начальный индекс - откуда начинать вырезать, и конечный индекс - до куда вырезать. Java中String. The substring begins at the specified beginIndex and extends to the character Provides detailed reference for the String class in Android, including methods and usage examples. substring ()으로 문자열을 자르는 방법을 알아보겠습니다. substring은 2가지 방식의 인자값을 받고 있으며 방식은 아래와 같다. split() String test = FullName. You can use/apply this method on any given string. The goal is to calculate amount of occurrences of subStr in str. The substring begins with the character at Этот действительно полезный метод, доступный вам, называется substring. Guide to substring() Function in Java. Java에서 String 클래스는 하위 문자열을 추출하기 위한 두 가지 방법인 substring() 및 substr()을 제공합니다. Domina la programación con Java y ¡certifícate! JDK 1. (ie a dot) In java doc api, I can't seem to fin Puedes usar String. Mastering string manipulation is crucial for Java W3Schools offers free online tutorials, references and exercises in all the major languages of the web. In Java, the substring () method of the String class returns a substring from the given string. This method either takes 1 parameter or 2 parameters, i. This method is most useful when you deal with text manipulation, parsing, or data extraction. Substring Strings are immutable. Fazit und Ausblick Die substring ()-Methode stellt ein unverzichtbares Werkzeug in der Java-Programmierung dar. Dans cet article, découvrez les deux variantes. substring (int beginIndex) 形式 此方式用于提取从索 Javaのsubstringの使い方について解説しています。substringは任意の長さ分を切り出すことができるメソッドで、後ろから、先頭から、指定文字を切り出す The Java String substring() method is a versatile tool for extracting and manipulating substrings within strings. substring(1, 2); The class String includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for The java. substringメソッド 部分文字列を取得する – substringメソッド public String substring (int begin [,int end]) begin：開始位置 end：終了位置 substringメソッドを利用することで、文字列のbegin+1～end 在 String 中提供了两个截取字符串的方法，一个是从指定位置截取到字符串结尾，另一个是截取指定范围的内容。下面对这两种方法分别进行介绍。 1. On other hand, we can say substring is a subset of String. عند إستدعاء هذه الدالة عندنا خيارين: تحديد من أين تبدأ. println(myStr. Here you will find the explanation of how using these methods, find out how they work and get some beneficial examples. Mit der Substring-Methode in Java extrahieren Sie einen Teilstring aus einem größeren String. 자바 (Java)에서 문자열을 자르는 방법으로 substring을 제공하고 있다. 자바 스트링 클래스에는 사용하기 편리하도록 만들어놓은 여러 가지 함수가 있습니다. Примеры кода включены. substring() method in Java returns a portion of a string from a specified starting index to an (optional) ending index. out. 특히 문자열을 자르는 경우가 많은데 Java에서 제공하는 문자열 자르는 함수인 . com public String substring(int beginIndex, int endIndex) Returns a new string that is a substring of this string. In Java, the substring () method of the String class returns a substring from the given string. substring() ein? Wie funktioniert substring() intern, und wie hat sich die Implementierung im Laufe der Zeit Java substring explained with clear examples. Examine This Blog to Gain a Comprehensive Understanding of Java Substrings Through Examples. substring()用于截取子串，支持从指定位置到末尾或指定范围截取；String. Java String substring () Method with examples Last Updated: September 17, 2022 by Chaitanya Singh | Filed Under: java The substring () Learn Java substring() method to extract parts of strings using startIndex & endIndex. ОписаниеМетод substring () в Java имеет два варианта и возвращает новую строку, которая является подстрокой данной строки. substring() method in Java is used to extract a portion of a string. Finding the substring of a string is a Погружение в метод substring в Java: секреты работы со строками Java — это язык программирования, который славится своей мощной обработкой строк. Here we discuss syntax and working of substring() Function in Java along with examples and its code. With substring, one or two indexes can be specified. substring(0,4) will substring public String substring(int beginIndex) この文字列の部分文字列である文字列を返します。 部分文字列は指定されたインデックスで始まり、この文字列の最後までになります。 例 In Java, the `substring` method is a powerful tool for working with strings. substring (int beginIndex) 形式 此方式用于提取从索 在 String 中提供了两个截取字符串的方法，一个是从指定位置截取到字符串结尾，另一个是截取指定范围的内容。下面对这两种方法分别进行介绍。 1. Instead we must copy a range of characters (from a begin index to an end). It allows developers to extract a portion of a string based on specified indices. substring (start, end) Chars beginning at start Up to but not including end There is a more complex version of substring () that takes both start and end index A substring in Java is a subset of another string. Сам метод перегружен и Узнайте, как получить подстроку из заданной строки в Java между двумя индексами. Strings are immutable sequences of characters in Java, and the `substring` method allows These Java examples use the substring and subSequence methods. 在 Java 编程中，`String` 类是使用最为频繁的类之一，它提供了许多实用的方法来处理字符串。`substring` 方法就是其中一个非常有用的方法，它允许我们从一个字符串中提取子字符串。 String. The substring begins at the specified beginIndex and extends to the character Javaのsubstringメソッド についてまとめました。 substringメソッドとは 一言でいうと「文字列から部分文字列を抜き出す」事ができるメソッドです。 【説明】 substringメソッドの書き方 substring以 Javaプログラミングで、文字列操作は避けて通れない重要なテーマです。 そのなかでも、substringメソッドは特に頻繁に使用される機能の1 Основные операции со строками в языке программирования Java, разделение и соеднинение строк, замена в строке, метоы=ды split, replace, join Then substring uses the return value of lastIndexOf to extract the file name extension — that is, the substring from the period to the end of the string. str. substring (시작 인덱스, 종료 인덱스) = str 문자열의 시작인덱스 부터 종료 인덱스전까지 자른다. В этой статье разберёмся с методом substring в Java — тем самым, который позволяет вырезать куски из строки, как ножом по маслу. Этот метод позволяет получить один фрагмент Substring в Java позволяет извлекать подстроку из исходной строки. to/40qrMLG ⬅️ Java String substring() method returns substring of a given string. язык программирования Java язык Комментарии к коду: в этой строчке мы указали с помощью метода substring () , что будет The practical ways of using the useful substring functionality in Java - from simple examples to more advanced scenarios. String 클래스의 substring () 메소드를 사용하여 문자열을 자르는 방법을 소개합니다. This guide covers syntax, examples, performance tips, and best practices for handling substring Вы можете извлечь подстроку из объекта String, используя метод substring. Strings are immutable sequences of characters in Java, and the `substring` method allows In Java, the `substring` method is a powerful and widely-used tool for working with strings. Truncating a String Using the JDK Java provides a number of convenient ways to truncate a String. 7, substring holds the reference of the original character Java String substring Method: The substring() method returns a string that is a substring of this string. If an ending index is not Learn how to use Java’s substring method efficiently. That said, there is a nice mathematical 프로그램을 개발을 하다 보면 문자열 조작을 많이 하게 된다. How substring () Works Internally When you call substring(), Java creates a new String object that shares the same character array as the original string. Ideal for beginners looking to understand string manipulation efficiently. Java provides a substring method that comes in two variants, allowing developers to extract substrings with ease and flexibility. substringメソッドの使い方 文字列から指定した範囲の部分文字列を取得するには String クラスで用意されている substring メソッドを使用します。書式 This article is about substring () methods in Java language. substring()の使い方を知ることは、実用的なプログラムを作れるよ En este artículo te contamos qué es y como se usa el método substring en Java. Else abbreviate it to (substring (str, 0, max - abbrevMarker. Explore this blog to get an in-depth idea about substring in java with examples. substring(5); 5文字目（インデックス5）から最後までを取得する 「Java Programming」という文字列の 5 文字目は「P」なので、「Programming」が抽出される The substring() method of String values returns the part of this string from the start index up to and excluding the end index, or to the end of the string if no end index is supplied. Substring is returned based on the indexes that we pass while calling this method. Learn to use the substring () and length () methods that are part of the Java String class. 4, CharSequence was added, and somebody apparently realized that it would be useful to have the same functionality there, but Javaのsubstringで文字列を切り出すサンプルです。 目次 Java already provides an overload to the substring method which captures exactly this behavior. Для работы со строками в Java определен класс String, который предоставляет ряд методов для Java's substring method is an effective tool for obtaining substrings from existing strings. Stringクラスには様々なメソッドがあるが、文字列の中の一部を切り出すこともできる。このページではJavaで文字列の一部を切り出すために In java substring can be part of a String or a whole string as well. Learn beginIndex, endIndex, common pitfalls, StringIndexOutOfBoundsException, and string slicing patterns. Описание метода substring () в языке Java и пример получение символов из строки, начиная с указанного индекса. The repeated substrings can overlap with each other. Given a string s, find the longest substring that appears more than once in the string. Explore Java equivalents to Python’s string slicing and how to implement similar operations efficiently. We cannot delete characters from them to get a substring. Substring - функция, используемая для работы с подстроками в строке. Java provides some methods to find substring in string java. Wie setzt man die Methode String. This code assumes that the file name has a period Java الدالة substring() في جافا تعريفها ترجع String عبارة عن جزء (substring) من الـ String الذي قام باستدعائها. A quick guide to Java String API substring() method examples. Using String’s 개발을 하면서 문자열을 원하는 위치에서 잘라야 하는 경우가 있습니다. You'll find the String class' substring method helpful in completing this challenge. Обратите внимание, что String — это тип на основе массива символов, а первый The practical ways of using the useful substring functionality in Java - from simple examples to more advanced scenarios. substring(int,int) existed first, because String existed first. Covering popular subjects like HTML, CSS, JavaScript, Python, SQL, Java, and many, many more. Explore this tutorial to get an in-depth idea about substring in A substring is a part of a string, or in other words, a subset of another string. substring() trong Java - Học JAVA chi tiết nhất từ cơ bản đến nâng cao giúp bạn tìm hiểu, làm quen và biết được cách thức làm việc của ngôn ngữ lập trình JAVA. Notice this change in documentation for Java 8: When there is a positive-width match at the beginning of the input sequence then an empty leading substring is included at the beginning 8. substring(1, 2); The class String includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for 2. إذا قمنا فقط بتحديد أين تبدأ الـ substring How to: Extracting a substring in Java is straightforward using the `substring` method. substring(2,3); String d = cde. substr()则按起始位置和长度截取，支持负数索引及省略 Learn how to efficiently extract substrings from Java strings, including common use cases and best practices. In this guide, you will learn about the String substring() method in Java programming and how to use it with an example. A String variable contains a collection of characters surrounded by double quotes (""): Java’s substring method can be used to extract substrings from larger strings. 示例 Get your own Java Server 从字符串中返回一个子字符串 String myStr = "Hello, World!"; System. 生徒 「Javaで文字列の一部だけを取り出す方法ってありますか？」 先生 「良い質問ですね！Javaでは、 String クラスの substring メソッドを使って、簡単に文字列の一部分を取り substring() trong Java - Học JAVA chi tiết nhất từ cơ bản đến nâng cao giúp bạn tìm hiểu, làm quen và biết được cách thức làm việc của ngôn ngữ lập trình JAVA. Javaにおけるsubstringの基礎知識 Javaでの部分文字列の取得は、基本的にStringクラスのsubstringメソッドで行います。 基本となる書き方 In Java, the `substring` method is a powerful and widely-used tool for working with strings. تحديد من أين تبدأ و أين تنتهي. Substring в Java - это функция, которая позволяет извлекать подстроки из строковых переменных. These methods return the substring from this string. Почему это важно? Узнайте, как получить подстроку из заданной строки в Java между двумя индексами. Первая его форма такова: String substring(int A quick example and explanation of the substring() API of the standard String class in Java. String 클래스의 substring () 메소드는 The substring() method in Java is available in two variations, each serving to extract parts of a string based on different sets of parameters: substring(int beginIndex): This version takes a Java에서 java. Javaでの部分文字列の取得はString. substring()で行うのが基本です。String. Метод substring() возвращает часть строки от начального индекса до конечного (не включая его), или, если конечный индекс не указан, — до конца строки. The substring begins with the character at the specified index and extends to the end of this string or up to The substring starts at, and includes the character at the location of the first number given and goes to, but does not include the character at the last number given. substring(7, 12)); 自己动手试一试 » String c = "abc". | TheDeveloperBlog. Применение Substring в Java с примерами кода. In Java, extracting substrings is a common operation used for text processing, data validation, and string The substring() method extracts characters, between two indices (positions), from a string, and returns the substring. lang API 提供了大量辅助工具，尤其是字符串操作方法。 在这个 Learn how to use substring() in Java with clear syntax, working examples, and practical use cases. Explore this blog on Substring Java meaning, types, methods, uses, working, syntax, examples Want to know how to extract a Java Substring? This tutorial provides you with code examples & walkthroughs of various methods to get a Java: Getting a substring from a string starting after a particular character Asked 13 years, 2 months ago Modified 1 year, 11 months ago Viewed 638k times The substring() method in Java is a useful String manipulation tool for extracting substrings from a larger String. 제임스 입니다. Index 위와 같이 Index는 Découvrez comment maîtriser efficacement la méthode substring en Java ! Guide complet, exemples pratiques et solutions aux erreurs Java substring() method returns a ‘substring’ of the specified string. Die gängigsten Aktionen für Strings in Java sind Verkettung, Abrufen eines Zeichens nach Index und Abrufen eines Teilstrings (Substrings). Mit ihr können Sie präzise und effizient Teilstrings extrahieren, was in Like a skilled surgeon, the substring method in Java can precisely cut out the parts you need from a string. a. Understanding its syntax, use cases, and common pitfalls will help How to use Java's String. The ability to extract parts of a string, known as substring extraction, is a common and Java’s substring method can be used to extract substrings from larger strings. Learn about the Java String <code>substring ()</code> method, how to use it with different parameters, and see practical examples. Now, Java will start at character two in the In Java, strings are a fundamental data type used to represent sequences of characters. ️ My Amazon Affiliate Link: https://amzn. String. substring(1, 2); The class String includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for Java String (字符串) 方法Java String substring ()方法从字符串中提取一个子字符串并返回它。substring ()方法的语法为：string. 각각 예제를 통해 어떻게 문자열을 자르는지 알아보겠습니다. A substring is a part of another string. This guide will cover the method's usage, how it works, examples. substring(0, 5), then I just get a new string s = "Hello". Until Java 1. 8で書いています。 Stringクラスのsubstring Stringクラスには、文字列の一部を切り出すsubstringメソッドがあります。引数の数に応じて2種類の切り出し方をしてくれます。 引 Finding a substring within a string is a common task in Java. ghi I would like to extract the substring before the first . Simple substring (start) v1 -- previous video str. This method returns a String datatype which corresponds to a portion of the Java Strings Strings are used for storing text. This method is most useful when you deal with Learn how to use the String class to represent and manipulate character strings in Java programs. Внутреннее устройство объектов String: экскурс в JDK 6 — Помнишь, я тебе обещала небольшой экскурс в историю Java? Разумеется, в контексте нашей темы, а именно — особенностей Java, being a versatile and widely-used programming language, provides a rich set of functionalities for handling strings. Узнайте, как выделить нужную часть строки, задав начальный и конечный индексы. Для работы со строками в Java определен класс String, который предоставляет ряд методов для Что такое метод substring в Java? Метод substring является частью класса String в Java. This method has two variants and returns a new string that is a substring of this string. substring() is used to get the portion of the string based on the index. Let’s take a look. substring(1, 2); The class String includes methods for examining individual characters of the sequence, for comparing strings, for searching strings, for Метод substring () в Java. substring (intstartIndex,intendInd W3Schools offers free online tutorials, references and exercises in all the major languages of the web. def. lang. Complete Learn to find the substring of a string between the begin and end indices, and valid values for both indices with examples. As a result, it extracts and retrieves a substring (part of a 作为 Java中String 类的重要方法之一， substring() 在字符串处理中扮演着重要的角色。然而，其底层实现原理往往被忽略，本文将深入探 Get Substring from a String in Java Asked 8 years, 10 months ago Modified 8 years, 10 months ago Viewed 13k times Java String class has two substring methods – substring (int beginIndex) and substring (int beginIndex, int endIndex). Пример кода для сохранения первых символов и дополнения. See the syntax, parameters, return value, and examples of the method. Java 中 substring()方法通过共享原字符串字符数组提取子串，节省内存、提性能。有获取到末尾和指定范围两种，创建新对象但共享数组。注意索引不越界，原字符串修改不影响子串，合 안녕하세요.
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