Text to array java

Преобразование строки в массив символов в Java

В этом посте мы обсудим, как преобразовать строку в массив символов в Java.

1. Наивное решение

Наивное решение состоит в том, чтобы использовать обычный цикл for, чтобы прочитать все символы в строке и присвоить их массиву символов один за другим. Этот подход очень эффективен для небольших строк.

результат:

[J, a, v, a]

2. Использование String.toCharArray() метод

Мы можем преобразовать строку в массив символов, используя String.toCharArray() метод, как показано ниже:

результат:

[J, a, v, a]

3. Использование отражения

Для длинных строк ничто не сравнится с отражением с точки зрения производительности. Мы можем проверить любую строку, используя отражение, и получить доступ к резервному массиву указанной строки.

результат:

[J, a, v, a]

Это все о преобразовании строки в массив символов в Java.

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Convert String to Array in Java

Strings in Java are objects which represent a sequence of characters. Java Strings are immutable which implies their value cannot be changed once created.

To convert a String to a char array, we can use a simple for loop or toCharArray() method.

String array in Java is an array of Strings. Arrays in Java are of fixed length. We can convert a String to an array using any one of the following ways: String.split() , Pattern.split() , String[] <> , and toArray() .

Introduction

Strings in Java are objects of String class which are nothing but a sequence of characters. Strings are immutable in Java which implies when we modify the value of a String, a new String object is created instead of modifying the value of the existing String object. We can import String class in Java from the java.lang package.

Java array is an object which contains elements of a similar data type. Additionally, The elements of an array are stored in a contiguous memory locations. The size of arrays cannot be changed in Java which implies an array is a set of fixed number of elements.

In this article, we will go through character and string arrays in Java.

Convert a String to Character Array in Java

There are two different ways to covert a String object to a character array in Java:

1. Naive Approach

A simple method is to read all of the characters in the string and assign them one by one to a Character array using a standard for-loop.

Detailed Procedure:

1. Get the string.
2. Create a character array that is the same length as the string.
3. Copy the character at the i t h i^ i t h position of the string to the i t h i^ i t h index of the array by traversing the string.
4. Return or perform the operation on the character array.

2. Using toCharArray() Method

To convert a string to a char array, we can use the toCharArray() function.

Detailed Procedure:

1. Get the string.
2. Call the toCharArray() method and store the character array returned by it in a character array.
3. Return or perform operation on the character array.

Converting String to String Array in Java

We’ll learn how to convert a string to an array of strings in Java in this section.

In Java, there are four ways to convert a String to a String array:

• Using String.split() Method
• Using Pattern.split() Method
• Using String[ ] Approach
• Using toArray() Method

Using String.split() Method

The String.split() method is used to split a string into distinct strings based on the delimiter provided (whitespace or other symbols). These entities can be directly stored in a string array.

Consider the following example, which shows how to convert a string to array in Java using the String.split() method.

Example 2: We changed the string to array in Java in the following example using the # delimiter.

Using Pattern.split() Method

The Pattern.split() method uses a regular expression(pattern) as the delimiter to split a string into an array of strings.

To use the technique, we have to import the Pattern class into our Java code as shown in the code below. This Pattern class can compile complex regex expressions.

Consider the following example, in which we will split a string into an array by using whitespace as the delimiter.

Example 2: We may also use any string or pattern as a delimiter to break a string into an array. We’ve used the &d& delimiter here.

Using String[ ] Approach

We can convert a string to string array by simply passing the string in the curly brackets of String [] <> . The impact of this conversion is that a String array will be created containing a single element — the input string itself.

Consider the following example, which shows how to convert a string to an array in Java using the String[] <> approach.

Using toArray() Method

The toArray() function of the List class can also be used to convert a string to array in Java. It takes a list of type String as the input and converts each entity into an element of a string array.

Consider the following example where we have converted the list of strings into a string array.

Conclusion

• In Java, the string is basically an object that represents a sequence of char values. An array of characters works the same as Java string.
• Strings are immutable in Java.
• A Java array is an object which contains elements of a similar data type. Arrays in Java are of fixed length.
• We can convert a String to a character array using either a naive for loop or the toCharArray() method.
• To convert a string to a string array based on a delimeter, we can use String.split() or Pattern.split() methods.
• We can also convert a string to an array containing the string as the only element by passing the string inside the curly brackets in String[] <> approach.
• To convert a list of strings in Java to a string array, we can use the toArray() method of List class.

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Convert String to Array in Java

When developing applications in Java there are many cases where we will find ourselves converting data from one type to the other.

Developers must understand how this is done because it will enhance their system effectiveness leading to ease of use from different users interacting with the system.

How to convert String to Array in Java

In this tutorial, we will learn how to convert String to array in Java and an example use case in an application is when we want to break the input search into several sequences and return results based on a sequence that matches a record from our data source.

A String is a data type that is implemented by a sequence of characters in double-quotes such as «Hello! World» while an array is a data structure that allows us to insert, traverse, delete, and search elements of a particular data type.

Using toArray() method of Set

A Set is a collection that only supports unique elements and it provides us with a method that we can leverage to convert a string to an array.

This method is called toArray() and is a generic method which means it can also be applied to other data types in Java.

To achieve this we will create a new array of size 0 and pass it to this method. The collection of elements in the Set will be added to this array and the method will return an array containing our elements.

Note that if the array created is less than the size of the collection the method creates a new array with the same size as the collection to accommodate all the values and returns the new array.

If the size of the array is large than the size of the collection the remaining storage locations are set to null .

The type of array returned by this method is of the same type as that of the specified array and the method throws an ArrayStoreException if the specified array type is not a supertype of every element in the collection.

The method also throws a NullPointerException if the specified array is null.

Using the split() method of String class

The split() method of the Stringg class uses a regular expression to split the string by every string that matches the specified regular expression.

The splitting is done by terminating a string with another substring that matches the given regular expression.

The method returns an array consisting of the terminated substrings and the elements are arranged in the order they appear in the original string.

If the regular expression does not match any substring the resulting array has only one element which is this string.

If the regular expressions syntax cannot be recognized the method throws a PatternSyntaxException .

Further reading:

Declare String array in java

How to convert String to Char Array in java

Using StringTokenizor class

From the name of the class, we can conclude that this class provides the functionality to break a string into tokens.

Tokens is a term mostly in programming to refer to a single element such as an identifier, keyword, constants, operators, and separators.

Note that the StringTokenizer cannot differentiate between identifiers, numbers, quoted strings, or how to jump comments but uses delimiters to break the string into tokens.

We will use this functionality to convert our string to an array by fetching each token obtained from our string and adding it to a new array.

Since we want to break our string using a whitespace delimiter, we will pass string whitespace in the second parameter of the StringTokenizer .

The size of our array will be managed by the countTokens() method of the StringTokenizer that returns an int value indicating the number of tokens that are remaining in the string.

We will use a while loop that will consume the hasMoreTokens() method checks if there are more tokens in the string and returns true if there is at least one element and false otherwise.

When the condition evaluates to true we use the nextToken() method to get the next element and add it to our new array.

A counter starting from 0 is used to increment the loop and we also use the counter value as the index of the element in our array.

Note that the use of StringTokenizer is discouraged in new code and it is only maintained for compatibility reasons because it is a legacy class.

The split() method which is discussed in this tutorial, should be used as an alternative to achieving similar functionality.

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How to Convert String to Array in Java

While we believe that this content benefits our community, we have not yet thoroughly reviewed it. If you have any suggestions for improvements, please let us know by clicking the “report an issue“ button at the bottom of the tutorial.

Sometimes we have to split String to array based on delimiters or some regular expression. For example, reading a CSV file line and parsing them to get all the data to a String array. In this tutorial, we will learn how to convert String to Array in Java program.

String to Array in Java

String class split(String regex) can be used to convert String to array in java. If you are working with java regular expression, you can also use Pattern class split(String regex) method. Let’s see how to convert String to an array with a simple java class example.

package com.journaldev.util; import java.util.Arrays; import java.util.regex.Pattern; public class StringToArrayExample < /** * This class shows how to convert String to String Array in Java * @param args */ public static void main(String[] args) < String line = "My name is Pankaj"; //using String split function String[] words = line.split(" "); System.out.println(Arrays.toString(words)); //using java.util.regex Pattern Pattern pattern = Pattern.compile(" "); words = pattern.split(line); System.out.println(Arrays.toString(words)); >> 

[My, name, is, Pankaj] [My, name, is, Pankaj] 

Note that Java provides a legacy class StringTokenizer also but you should not use it because it doesn’t have an option for a regular expression and using it is confusing. We can use Java regular expressions also to split String into String array in java, learn more about java regular expression.

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