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What You Need to Know About Using Strings in Java

Once you start learning Java, the String class will capture your attention, thanks to its unique properties.

You can create and manipulate strings in Java more easily than other languages. That’s because the String class offers various features.

Based on these features, there are several methods to generate and edit strings depending upon your preferences and needs. Similarly, a lot will depend on your application and where strings need to be used.

How Are Java Strings Different?

If you have previously worked with C language, you know that strings in C are an array of chars (characters). On the other hand, Java strings are immutable and contain Unicode characters.

One of the key features that make strings in Java unique is concatenation. Just use the addition operator “+” to join two or more strings. This is something you can’t do with other Java objects, such as Point or Circle.

Also, as mentioned before, Java Strings are immutable, i.e. you can’t modify them. For instance, methods like toUpperCase() and toLowerCase() generate a completely new string, instead of making changes to the existing string contents. Now your code will return this newly-generated string.

Related: How to Manipulate Text in PHP With These Functions

Another area where strings are different is when it comes to using null characters for terminating strings in languages like C. In Java, strings are objects supported by character arrays. If you are looking to read your string’s contents in the way character arrays represent them, using the toCharArray() method will do the job.

Comparing strings in Java is also more convenient than in other programming languages. Rather than writing a lengthy block of code for comparing strings, you can use the equals() method to compare two or more strings used in any program. This is mainly because, in Java, the equals method is overridden by the String class, which makes string comparison a piece of cake.

On a similar note, searching within substrings in Java is hassle-free as well. While using regular expressions or methods like lastIndexOf() and indexOf(), you can search segments of strings and return values once a match is identified. You can also use regular expressions to trim and split different strings and use them individually for a wide range of uses in any program.

How Are Strings Stored In the Memory?

Now that you know what makes strings in Java different and beneficial, let’s explore the String class. If you know a thing or two about memory management in Java, then you must have dealt with its two key entities: heap and stack.

The stack is used to execute processes and operations after being called by a Java program, whereas heap stores content – needed to run and execute code effectively. So, how is memory management relevant in the case of strings?

That’s because the String class and string literals in Java receive different treatment. This indicates that string literals are assigned unique storage space in the heap memory, referred to as the String Constant Pool. Therefore, whenever you use string literals to create string objects in Java, the String Constant Pool stores them.

On the contrary, when you use the new keyword to create string objects, Java will treat them just like any other object and send them to the heap for storage.

String Literals Example

Now that you know enough about string objects, let’s go through an example of string literals:


public class muostrings {
public static void main(String args[])
{
String himuo = "Hello World from MUO";
System.out.println (himuo);
}
}
Strings literal

Here, the string literal created the String object with contents “Hello World from MUO”. Java will send this object to the String Constant Pool.

Using the New Keyword

You can also use the new keyword to generate String objects.

The string object of the string “himuo” with contents “Hello World from MUO” has been generated by a string literal and will be sent to the String Constant Pool. Similarly, string objects can also be created using the new keyword as follows:


public class muostringsobj {
public static void main(String args[]) {
char[] strArr = { 'M', 'O', 'U'};
String jStr = new String(strArr);
System.out.println( jStr );
}
}
String Object Program

The above example uses the new keyword to create a string object. As explained previously, they are sent to the heap, where they are stored with other variables and objects waiting to be executed by the program.

By now, you must be curious about the String Constant Pool, and rightly so. It allocates pool space to objects based on the string object’s contents. After the String Constant Pool receives objects, it checks them to verify whether two objects contain exactly the same content.

Can Two String Objects Store Same Contents?

When a string literal is used to create a new object, Java Virtual Machine (JVM) reviews the object contents and evaluates whether it already exists in the pool. When an object contains content that is already present in the pool, the object’s reference is returned without creating the new object. If you must create the new object, you have to make sure that the content is distinct and unique.

However, if you use the new keyword to create a new string, it will be processed differently. When you use the new keyword to create a new string, it will be generated, irrespective of whether it contains the same contents as the existing string.

This indicates that two existing strings objects stored in the heap memory are allowed to entail the same contents; this is different from string objects stored in the String Constant Pool. You can also prove this with the “==” operator; it returns true if two objects with the same physical address are compared.


public class comparingStrngs {
public static void main(String[] args)
{
String firstLiteral = "muo1";
String secondLiteral = "muo1";
System.out.println(firstLiteral == secondLiteral);
String firstKeyword = new String("muo2");
String secondKeyword = new String("muo2");
System.out.println(firstKeyword == secondKeyword);
}
}
String Comparison

Now You Can Understand Strings In Java Easily

In this article, you learned how strings in Java are different, ways to use strings in Java, memory management of strings in Java, and other important details on how strings work. To test your understanding, why not write a Java program to concatenate two strings?

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