How to declare string methods in java

Safalta Expert Published by: Vanshika Jakhar Updated Sat, 19 Nov 2022 09:56 AM IST

A non-primitive data type is a string. Almost every programming language uses it as an array of characters. Java, however, implements strings as objects of type String, in contrast to the majority of programming languages that do so.
A character string is represented by the predefined String class in Java. In Java programs, every string literal, including "Hello," is implemented as an instance of this class. Strings can be implemented as built-in objects in Java, which can offer a comprehensive set of features that make string manipulation simpler.

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Among other things, it has methods for concatenating two strings, finding a substring, and comparing two strings. 

Table of Content
What do Java Strings mean?
Java's creation of strings
String methods in Java
Fellow classes of Java String

What do Java Strings mean?

A string is recognized by Java as a class and not as a datatype. Even in Java, Strings can be created by simply instantiating the String Class found in java.lang package. The Java string class offers a selection of constructors and methods for creating, modifying, and searching strings.
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Java's creation of strings

Let's first learn how to create strings before delving deeply into how they function in Java.
In Java, string objects can be created in one of the following two ways:
  • By a string constructor
  • By a string literal 
By string function 
There are numerous constructors available for Java's String class. The JVM creates a new string object outside the constant string pool in the heap area when we create a string object using constructors. Although the variable refers to the object in the heap area, the literal is placed in the string constant pool.

The following is an explanation of some significant string class constructors:

  • The default function Object() can be used to produce an empty String.

  • Creating strings with initial values is a common task.
  • Additionally, we can use the function Object() { [native code] } to specify a portion of a character array as an initializer.
  • Using a constructor, we can produce an object of type String that has the same character set as another String object.
By a string literal
This is the simplest method for creating strings in Java. Double quotes can be used to create string literals.
What is the internal working of this?
The idea of a "string constant pool" is used in Java to make strings efficient. Every time we create a string literal, the JVM checks the string constant pool. If the string is present in the pool already, a reference to the pooled object is returned. If the string is missing, a new instance of it is created and added to the pool of string constants.

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String methods in Java

A few Java string methods that can each be further explained are listed below. Here they are:
  • String substring(int beginIndex): Returns the first substring starting at the given index.
  • int length() returns the length of the string.
  • String substring(int beginIndex, int endIndex): This function returns the substring at the specified begin and end indexes.
  • static String format: This function produces a formatted string that matches the specified locale.
  • boolean equals(Object obj): If the string matches the specified, it returns a true value; otherwise, it returns a false value.
  • boolean startsWith(String prefix)- Depending on the string's specified prefix, this function either returns true or false.
  • boolean ends with(String suffix) determines whether a given string contains the given suffix at the end.
  • The string's hash code is returned by the int hashCode() function.
  • String intern(): This function returns the given String's canonical representation.
  • Lowercase characters are produced by the function string toLowerCase(), which returns a string.
  • A string with uppercase characters is produced by the function string toUpperCase().
  • The function subSequence() extracts a subsequence from the string.
  • The function toCharArray() turns a string into a character array.
  • isEmpty() determines whether or not a string is empty.
  • String trim() removes the string's beginning and ending tails.
  • String matches() determines whether the given string matches the given regex.

Fellow classes of Java String

A large library of classes and packages is available in Java. Fellow Java String class classes include StringBuffer and StringBuilder. They offer various string functionality. A string is less dynamic because it supports fixed-length, immutable character sequences. On the other hand, these classes represent mutable character sequences.

String Buffer
  • Similar to a String, a string buffer allows for modifications.
  • It contains a string of characters, but the class's various methods allow you to alter the length and content of the string.
  • Thread-safe buffers for strings exist. The append and insert methods are the main operations on a StringBuffer.

String Builder
  • Similar to String objects, StringBuilder objects can also be modified.
  • Internally, these objects are treated as character-sequence-containing variable-length arrays. The length and content of the sequence are always subject to change by method invocations.
  • As a replacement for StringBuffer, the String Builder class offers an API that is compatible with StringBuffer.

What makes strings unique in Java?

Java strings are an object of the Java String class, making them more than just a non-primitive data type. A char array internally implements it. Strings cannot be modified, just like arrays cannot. A brand-new String must be created to convert to one.

What distinguishes a string from a string buffer?

The classes String and StringBuffer are both immutable. A string takes up more memory and runs slowly. StringBuffer, on the other hand, is quick and uses less memory.

Is Java thread-safe for strings?

Because strings cannot be changed, they are thread-safe. Two threads cannot use the string at the same time.

Why can't strings be changed in Java?

Making the string class immutable has benefits for caching, security, synchronization, and efficiency. The previously mentioned basic justifications for string immutability.

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