String to char массиве 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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4 Different Ways to Convert String to Char Array in Java

The String in java represents a stream of characters. There are many ways to convert string to character array.

Java Convert String to char Array

1. Manual code using for loop
2. String toCharArray() method
3. String getChars() method for subset
4. String charAt() method

Let’s look into some examples to convert string to char array in Java.

1. Using for loop

We can write our own code to get the string characters one by one. Then populate the char array with the characters.

String s = "abc123"; char[] chrs = new char[s.length()]; for (int i = 0; i < s.length(); i++) chrs[i] = s.charAt(i); System.out.println(Arrays.toString(chrs));

Output: [a, b, c, 1, 2, 3]

This method is useful when you want to have some additional logic to populate the char array. For example, skipping duplicate characters or changing them to lowercase, etc.

2. toCharArray() method

This is the recommended method to convert string to char array. Let’s look at the example to convert string to char array using toCharArray() method. We will use JShell to run the code snippets.

jshell> String s = "abc123"; s ==> "abc123" jshell> char[] chars = s.toCharArray(); chars ==> char[6] < 'a', 'b', 'c', '1', '2', '3' >jshell> System.out.println(Arrays.toString(chars)); [a, b, c, 1, 2, 3] jshell>

3. charAt() method

Sometimes we have to get the character at the specific index. We can use charAt() method for this.

jshell> String s = "Java"; s ==> "Java" jshell> char c = s.charAt(3); c ==> 'a'

4. getChars() method

This method is useful when we want to copy characters between specific indices. String getChars() method copies the characters from the string to the destination character array. The method syntax is:

public void getChars( int srcBegin, int srcEnd, char dst[], int dstBegin)

Let’s understand the significance of each of the method arguments.

1. srcBegin: index from where the characters will be copied.
2. srcEnd: index at which copying will stop. The last index to be copied will be srcEnd-1.
3. dst: The destination character array. It should be initialized before calling this method.
4. dstBegin: The start index in the destination array.

Let’s look at an example of getChars() method.

String s = "abc123"; char[] substringChars = new char[7]; s.getChars(1, 4, substringChars, 2); System.out.println(Arrays.toString(substringChars));

Output: [, , b, c, 1, , ]

The string characters are copied from index 1 to 3. The characters are copied starting from 2nd index of the destination array.

If the destination array size is smaller than the required size, java.lang.StringIndexOutOfBoundsException is thrown.

Conclusion

• String toCharArray() is the recommended method to convert string to char array.
• If you want to copy only a part of the string to a char array, use getChars() method.
• Use the charAt() method to get the char value at a specific index.
• You can write your own code to convert string to char array if there are additional rules to be applied while conversion.

References:

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String to char array java - convert string to char

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 convert String to the character array in java programs or convert a string to char from specific index.

String to char Java

String class has three methods related to char. Let’s look at them before we look at a java program to convert string to char array.

1. char[] toCharArray() : This method converts string to character array. The char array size is same as the length of the string.
2. char charAt(int index) : This method returns character at specific index of string. This method throws StringIndexOutOfBoundsException if the index argument value is negative or greater than the length of the string.
3. getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) : This is a very useful method when you want to convert part of string to character array. First two parameters define the start and end index of the string; the last character to be copied is at index srcEnd-1. The characters are copied into the char array starting at index dstBegin and ending at dstBegin + (srcEnd-srcBegin) - 1.

Let’s look at a simple string to char array java program example.

package com.journaldev.string; public class StringToCharJava < public static void main(String[] args) < String str = "journaldev"; //string to char array char[] chars = str.toCharArray(); System.out.println(chars.length); //char at specific index char c = str.charAt(2); System.out.println(c); //Copy string characters to char array char[] chars1 = new char[7]; str.getChars(0, 7, chars1, 0); System.out.println(chars1); >> 

In above program, toCharArray and charAt usage is very simple and clear. In getChars example, first 7 characters of str will be copied to chars1 starting from its index 0. That’s all for converting string to char array and string to char java program. Reference: API Doc

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String to char array java - convert string to char

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 convert String to the character array in java programs or convert a string to char from specific index.

String to char Java

String class has three methods related to char. Let’s look at them before we look at a java program to convert string to char array.

1. char[] toCharArray() : This method converts string to character array. The char array size is same as the length of the string.
2. char charAt(int index) : This method returns character at specific index of string. This method throws StringIndexOutOfBoundsException if the index argument value is negative or greater than the length of the string.
3. getChars(int srcBegin, int srcEnd, char dst[], int dstBegin) : This is a very useful method when you want to convert part of string to character array. First two parameters define the start and end index of the string; the last character to be copied is at index srcEnd-1. The characters are copied into the char array starting at index dstBegin and ending at dstBegin + (srcEnd-srcBegin) - 1.

Let’s look at a simple string to char array java program example.

package com.journaldev.string; public class StringToCharJava < public static void main(String[] args) < String str = "journaldev"; //string to char array char[] chars = str.toCharArray(); System.out.println(chars.length); //char at specific index char c = str.charAt(2); System.out.println(c); //Copy string characters to char array char[] chars1 = new char[7]; str.getChars(0, 7, chars1, 0); System.out.println(chars1); >> 

In above program, toCharArray and charAt usage is very simple and clear. In getChars example, first 7 characters of str will be copied to chars1 starting from its index 0. That’s all for converting string to char array and string to char java program. Reference: API Doc

Thanks for learning with the DigitalOcean Community. Check out our offerings for compute, storage, networking, and managed databases.

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String to Char Array Java Tutorial

Thanoshan MV

In this article, we’ll look at how to convert a string to an array of characters in Java. I'll also briefly explain to you what strings, characters, and arrays are.

What is a Character in Java?

Characters are primitive datatypes. A character is a single character enclosed inside single quotation marks. It can be a letter, a digit, a punctuation mark, a space or something similar. For example:

What is a String in Java?

Strings are objects (reference type). A string is made up of a string of characters. It's anything inside double quotation marks. For example:

What is an Array in Java?

Arrays are fundamental data structures which can store fixed number of elements of the same data type in Java. For example, let's declare an array of characters:

Now, we have a basic understanding about what strings, characters, and arrays are.

Let's Convert a String to a Character Array

1. Use toCharArray() Instance Method

toCharArray() is an instance method of the String class. It returns a new character array based on the current string object.

Let's check out an example:

// define a string String vowels = "aeiou"; // create an array of characters char[] vowelArray = vowels.toCharArray(); // print vowelArray System.out.println(Arrays.toString(vowelArray));

When we convert a string to an array of characters, the length remains the same. Let's check the length of both vowels and vowelArray :

System.out.println("Length of \'vowels\' is " + vowels.length()); System.out.println("Length of \'vowelArray\' is " + vowelArray.length);

Length of 'vowels' is 5 Length of 'vowelArray' is 5

We can use various ways to print an array. I used the toString() static method from the Arrays utility class.

You can read more about the toCharArray() instance method in the Java documentation.

2. Use charAt() Instance Method

charAt() is an instance method of the String class. It returns a character at the specified index of the current string.

NOTE: a string is zero index based, similar to an array.

Let's see how we can convert a string to an array of characters using charAt() :

// define a string String vowels = "aeiou"; // create an array of characters. Length is vowels' length char[] vowelArray = new char[vowels.length()]; // loop to iterate each characters in the 'vowels' string for (int i = 0; i < vowels.length(); i++) < // add each character to the character array vowelArray[i] = vowels.charAt(i); >// print the array System.out.println(Arrays.toString(vowelArray));

You can read more about the charAt() instance method in the Java documentation.

I just showed you another way of converting a string to a character array, but we can use the toCharArray() method to easily convert instead of creating loops and iterating them.

Please feel free to let me know if you have any suggestions or questions.

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