{"id":1189,"date":"2022-02-24T20:17:55","date_gmt":"2022-02-24T20:17:55","guid":{"rendered":"https:\/\/mdr.foobrdigital.com\/?p=1189"},"modified":"2022-02-24T20:17:55","modified_gmt":"2022-02-24T20:17:55","slug":"java-strings","status":"publish","type":"post","link":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/2022\/02\/24\/java-strings\/","title":{"rendered":"Java Strings"},"content":{"rendered":"\n

In this tutorial, we will learn about Java strings, how to create them, and various methods of the String class with the help of examples.<\/p>\n\n\n\n

In Java, a string is a sequence of characters. For example, “hello”<\/var> is a string containing a sequence of characters ‘h’<\/var>, ‘e’<\/var>, ‘l’<\/var>, ‘l’<\/var>, and ‘o’<\/var>.<\/p>\n\n\n\n

We use double quotes<\/strong> to represent a string in Java. For example,<\/p>\n\n\n\n

\/\/ create a string\nString type = \"Java programming\";<\/code><\/pre>\n\n\n\n
Here, we have created a string variable named type<\/var>. The variable is initialized with the string Java Programming<\/code>.<\/p>\n\n\n\n
\n\n\n\n
Example: Create a String in Java<\/h3>\n\n\n\n
class Main {\n  public static void main(String[] args) {\n    \n    \/\/ create strings\n    String first = \"Java\";\n    String second = \"Python\";\n    String third = \"JavaScript\";\n\n    \/\/ print strings\n    System.out.println(first);   \/\/ print Java\n    System.out.println(second);  \/\/ print Python\n    System.out.println(third);   \/\/ print JavaScript\n  }\n}<\/code><\/pre>\n\n\n\n
In the above example, we have created three strings named first<\/var>, second<\/var>, and third<\/var>. Here, we are directly creating strings like primitive types.<\/p>\n\n\n\n
However, there is another way of creating Java strings (using the new<\/code> keyword). We will learn about that later in this tutorial.<\/p>\n\n\n\n
Note<\/strong>: Strings in Java are not primitive types (like int<\/code>, char<\/code>, etc). Instead, all strings are objects of a predefined class named String<\/code>.<\/p>\n\n\n\n
And, all string variables are instances of the String<\/code> class.<\/p>\n\n\n\n
\n\n\n\n
Java String Operations<\/h2>\n\n\n\n
Java String provides various methods to perform different operations on strings. We will look into some of the commonly used string operations.<\/p>\n\n\n\n
1. Get length of a String<\/h3>\n\n\n\n
To find the length of a string, we use the length()<\/code> method of the String. For example,<\/p>\n\n\n\n
class Main {\n  public static void main(String[] args) {\n\n    \/\/ create a string\n    String greet = \"Hello! World\";\n    System.out.println(\"String: \" + greet);\n\n    \/\/ get the length of greet\n    int length = greet.length();\n    System.out.println(\"Length: \" + length);\n  }\n}<\/code><\/pre>\n\n\n\n
Output<\/strong><\/p>\n\n\n\n
String: Hello! World\nLength: 12<\/samp><\/code><\/pre>\n\n\n\n
In the above example, the\u00a0length()<\/code>\u00a0method calculates the total number of characters in the string and returns it.<\/p>\n\n\n\n
\n\n\n\n
2. Join Two Java Strings<\/h3>\n\n\n\n
We can join two strings in Java using the concat()<\/code> method. For example,<\/p>\n\n\n\n
class Main {\n  public static void main(String[] args) {\n\n    \/\/ create first string\n    String first = \"Java \";\n    System.out.println(\"First String: \" + first);\n\n    \/\/ create second\n    String second = \"Programming\";\n    System.out.println(\"Second String: \" + second);\n\n    \/\/ join two strings\n    String joinedString = first.concat(second);\n    System.out.println(\"Joined String: \" + joinedString);\n  }\n}<\/code><\/pre>\n\n\n\n
Output<\/strong><\/p>\n\n\n\n
First String: Java \nSecond String: Programming     \nJoined String: Java Programming<\/samp><\/code><\/pre>\n\n\n\n
In the above example, we have created two strings named first<\/var> and second<\/var>. Notice the statement,<\/p>\n\n\n\n
String joinedString = first.concat(second);<\/code><\/pre>\n\n\n\n
Here, the concat()<\/code> method joins the second<\/var> string to the first<\/var> string and assigns it to the joinedString<\/var> variable.<\/p>\n\n\n\n
We can also join two strings using the\u00a0+<\/code>\u00a0operator in Java. <\/p>\n\n\n\n
\n\n\n\n
3. Compare two Strings<\/h3>\n\n\n\n
In Java, we can make comparisons between two strings using the equals()<\/code> method. For example,<\/p>\n\n\n\n
class Main {\n  public static void main(String[] args) {\n\n    \/\/ create 3 strings\n    String first = \"java programming\";\n    String second = \"java programming\";\n    String third = \"python programming\";\n\n    \/\/ compare first and second strings\n    boolean result1 = first.equals(second);\n    System.out.println(\"Strings first and second are equal: \" + result1);\n\n    \/\/ compare first and third strings\n    boolean result2 = first.equals(third);\n    System.out.println(\"Strings first and third are equal: \" + result2);\n  }\n}<\/code><\/pre>\n\n\n\n
Output<\/strong><\/p>\n\n\n\n
Strings first and second are equal: true\nStrings first and third are equal: false<\/samp><\/code><\/pre>\n\n\n\n
In the above example, we have created 3 strings named first<\/var>, second<\/var>, and third<\/var>. Here, we are using the equal()<\/code> method to check if one string is equal to another.<\/p>\n\n\n\n
The\u00a0equals()<\/code>\u00a0method checks the content of strings while comparing them.<\/p>\n\n\n\n
Note<\/strong>: We can also compare two strings using the\u00a0==<\/code>\u00a0operator in Java. However, this approach is different than the\u00a0equals()<\/code>\u00a0method. To learn more, visit\u00a0Java String == vs equals().<\/p>\n\n\n\n
\n\n\n\n
Escape character in Java Strings<\/h2>\n\n\n\n
The escape character is used to escape some of the characters present inside a string.<\/p>\n\n\n\n
Suppose we need to include double quotes inside a string.<\/p>\n\n\n\n
\/\/ include double quote \nString example = \"This is the \"String\" class\";<\/code><\/pre>\n\n\n\n
Since strings are represented by double quotes<\/strong>, the compiler will treat “This is the “<\/var> as the string. Hence, the above code will cause an error.<\/p>\n\n\n\n
To solve this issue, we use the escape character \\<\/code> in Java. For example,<\/p>\n\n\n\n
\/\/ use the escape character\nString example = \"This is the \\\"String\\\" class.\";<\/code><\/pre>\n\n\n\n
Now escape characters tell the compiler to escape double quotes<\/strong> and read the whole text.<\/p>\n\n\n\n
\n\n\n\n
Java Strings are Immutable<\/h2>\n\n\n\n
In Java, strings are immutable<\/strong>. This means, once we create a string, we cannot change that string.<\/p>\n\n\n\n
To understand it more deeply, consider an example:<\/p>\n\n\n\n
\/\/ create a string\nString example = \"Hello! \";<\/code><\/pre>\n\n\n\n
Here, we have created a string variable named example<\/var>. The variable holds the string “Hello! “<\/var>.<\/p>\n\n\n\n
Now suppose we want to change the string.<\/p>\n\n\n\n
\/\/ add another string \"World\"\n\/\/ to the previous tring example\nexample = example.concat(\" World\");<\/code><\/pre>\n\n\n\n
Here, we are using the concat()<\/code> method to add another string World<\/var> to the previous string.<\/p>\n\n\n\n
It looks like we are able to change the value of the previous string. However, this is not true<\/code>.<\/p>\n\n\n\n
Let’s see what has happened here,<\/p>\n\n\n\n
  1. JVM takes the first string “Hello! “<\/var><\/li>
  2. creates a new string by adding “World”<\/var> to the first string<\/li>
  3. assign the new string “Hello! World”<\/var> to the example<\/var> variable<\/li>
  4. the first string “Hello! “<\/var> remains unchanged<\/li><\/ol>\n\n\n\n
    \n\n\n\n
    Creating strings using the new keyword<\/h2>\n\n\n\n
    So far we have created strings like primitive types in Java.<\/p>\n\n\n\n
    Since strings in Java are objects, we can create strings using the new<\/code> keyword as well. For example,<\/p>\n\n\n\n
    \/\/ create a string using the new keyword\nString name = new String(\"Java String\");<\/code><\/pre>\n\n\n\n
    In the above example, we have created a string name<\/var> using the new<\/code> keyword.<\/p>\n\n\n\n
    Here, when we create a string object, the\u00a0String()<\/code>\u00a0constructor is invoked. <\/p>\n\n\n\n
    Note<\/strong>: The\u00a0String<\/code>\u00a0class provides various other constructors to create strings. To learn more, visit\u00a0Java String (official Java documentation).<\/p>\n\n\n\n
    \n\n\n\n
    Example: Create Java Strings using the new keyword<\/h3>\n\n\n\n
    class Main {\n  public static void main(String[] args) {\n\n    \/\/ create a string using new\n    String name = new String(\"Java String\");\n\n    System.out.println(name);  \/\/ print Java String\n  }\n}<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    Create String using literals vs new keyword<\/h3>\n\n\n\n
    Now that we know how strings are created using string literals and the new<\/code> keyword, let’s see what is the major difference between them.<\/p>\n\n\n\n
    In Java, the JVM maintains a string pool<\/strong> to store all of its strings inside the memory. The string pool helps in reusing the strings.<\/p>\n\n\n\n
    1. While creating strings using string literals,<\/p>\n\n\n\n
    String example = \"Java\";<\/code><\/pre>\n\n\n\n
    Here, we are directly providing the value of the string (Java<\/code>). Hence, the compiler first checks the string pool to see if the string already exists.<\/p>\n\n\n\n
    • If the string already exists<\/strong>, the new string is not created. Instead, the new reference, example<\/var> points to the already existed string (Java<\/code>).<\/li>
    • If the string doesn’t exist<\/strong>, the new string (Java<\/code> is created.<\/li><\/ul>\n\n\n\n
      2. While creating strings using the new keyword,<\/p>\n\n\n\n
      String example = new String(\"Java\");<\/code><\/pre>\n\n\n\n
      Here, the value of the string is not directly provided. Hence, a new \"Java\"<\/code> string is created even though \"Java\"<\/code> is already present inside the memory pool.<\/p>\n\n\n\n
      \n\n\n\n
      Methods of Java String<\/h2>\n\n\n\n
      Besides those mentioned above, there are various\u00a0string methods\u00a0present in Java. Here are some of those methods:<\/p>\n\n\n\n
      Methods<\/th>Description<\/th><\/tr>
      contains()<\/td>checks whether the string contains a substring<\/td><\/tr>
      substring()<\/td>returns the substring of the string<\/td><\/tr>
      join()<\/td>join the given strings using the delimiter<\/td><\/tr>
      replace()<\/td>replaces the specified old character with the specified new character<\/td><\/tr>
      replaceAll()<\/td>replaces all substrings matching the regex pattern<\/td><\/tr>
      replaceFirst()<\/td>replace the first matching substring<\/td><\/tr>
      charAt()<\/td>returns the character present in the specified location<\/td><\/tr>
      getBytes()<\/td>converts the string to an array of bytes<\/td><\/tr>
      indexOf()<\/td>returns the position of the specified character in the string<\/td><\/tr>
      compareTo()<\/td>compares two strings in the dictionary order<\/td><\/tr>
      compareToIgnoreCase()<\/td>compares two strings ignoring case differences<\/td><\/tr>
      trim()<\/td>removes any leading and trailing whitespaces<\/td><\/tr>
      format()<\/td>returns a formatted string<\/td><\/tr>
      split()<\/td>breaks the string into an array of strings<\/td><\/tr>
      toLowerCase()<\/td>converts the string to lowercase<\/td><\/tr>
      toUpperCase()<\/td>converts the string to uppercase<\/td><\/tr>
      valueOf()<\/td>returns the string representation of the specified argument<\/td><\/tr>
      toCharArray()<\/td>converts the string to a char<\/code> array<\/td><\/tr>
      matches()<\/td>checks whether the string matches the given regex<\/td><\/tr>
      startsWith()<\/td>checks if the string begins with the given string<\/td><\/tr>
      endsWith()<\/td>checks if the string ends with the given string<\/td><\/tr>
      isEmpty()<\/td>checks whether a string is empty of not<\/td><\/tr>
      intern()<\/td>returns the canonical representation of the string<\/td><\/tr>
      contentEquals()<\/td>checks whether the string is equal to charSequence<\/td><\/tr>
      hashCode()<\/td>returns a hash code for the string<\/td><\/tr>
      subSequence()<\/td>returns a subsequence from the string<\/td><\/tr><\/tbody><\/table><\/figure>\n","protected":false},"excerpt":{"rendered":"
      In this tutorial, we will learn about Java strings, how to create them, and various methods of the String class with the help of examples. In Java, a string is a sequence of characters. For example, “hello” is a string containing a sequence of characters ‘h’, ‘e’, ‘l’, ‘l’, and ‘o’. We use double quotes to represent a string in Java. For example, Here, […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[484],"tags":[],"_links":{"self":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1189"}],"collection":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/comments?post=1189"}],"version-history":[{"count":0,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/posts\/1189\/revisions"}],"wp:attachment":[{"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/media?parent=1189"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/categories?post=1189"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mudassirbackup.infinitycodestudio.com\/index.php\/wp-json\/wp\/v2\/tags?post=1189"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}