Strings are important concepts in programming and are data types that allow storage of character sequences. String methods are built-in functions that are called on a string to either get information or manipulate data.
In Java, strings are treated as immutable data, therefore their values cannot be changed. To work with strings and perform operations on them, you need to understand string methods in Java and how they work.
This post serves as a guide for showing you what string methods are, why they’re important in Java, and how you can use them (providing syntax and examples). We’ll begin by explaining in simple terms what string methods are and how they work. After that, we’ll demonstrate how to work with immutable strings and optimize your applications. By the end of this article, you should have a working knowledge of string methods.
A string is a sequence of characters created by using string literals (double quotes). Strings are very important concepts in every programming language, including Java, because strings are useful in representing textual data. The machine will then interpret these data as binary to understand the instructions given. Strings are immutable—therefore, to manipulate a string, you have to make use of string methods. So, what are string methods in Java?
In simple terms, string methods are built-in functions that allow programmers to perform operations on strings. String methods are available in all programming languages just as they are in Java. With these methods, programmers can easily manipulate string data and convert string values.
String methods allow you to manipulate string data, which is very important in handling string data values. Below are some of the benefits of string methods.
This is just a portion of the important work string methods perform. Now let’s talk about how string methods work in Java and how you can use them.
In Java, you can use two methods to create a string. You can use string literals (wrapping string values with double quotes) or the new keyword.
To create a string with the string literal method, you create a string variable, and then give it a value wrapped with two double quotes, both on the right and left hand. Example:
String Greet = "Welcome Java";The example above will create a string object for the string “Greet” in the heap memory. This string object will be immutable to optimize memory space. So, if you create another instance of a string literal, the Java virtual machine (JVM) scans the heap memory for string objects with the same value. If JVM finds a string instance with the same value, it’ll simply allocate the new instance to the previous string object instead of creating a new memory address.
The second method of creating a string is by calling the new keyword and then passing the string value in double quotes. Example:
String Greet = new String("Welcome");Both string literal and new keyword will create immutable strings. This is where string methods come in. When strings methods are executed—for example, the concat() method—the JVM takes the value of the string and performs the manipulation by joining the two strings together.
In Java, there are about 50 different types of built-in string methods. These string methods make manipulation and working with strings easy. Following are examples of the most commonly used string methods, what you can use them for, and how you can use them.
This method is efficient in finding the length of a string, and you apply this method if you want to know the number of characters a string has. To make use of this method, you call it like this:
String Greet = "Hello!";
int Length = Greet.length( );
system.out.println("The length of the string Greet is:" + length);Notice that the Length variable has a type of int, which indicates that the value of the .length() method is an integer type. The code above will print the number of characters in the Greet variable, which is 6.
Sometimes you might want to update the case of your string data from either a lowercase letter to an uppercase letter or vice versa. For this purpose, you can make use of the .toUpperCase() or .toLowerCase methods. The .toUpperCase() method will check if the string data contains lowercase letters and convert them to uppercase.
String Greet = "Hello!";
String upperCase = Greet.toUpperCase( );
System.Out.Println(upperCase);The code above will print the text “HELLO!” instead of the original “Hello!” text. The .toLowerCase method does the opposite of the .toUpperCase(). So, if we make use of the .toLowerCase method, we’ll get “hello!” instead.
In a case where you want to know if the values of two strings match, you can make use of the .equals() method. This method compares two strings to know if they contain the same characters with the same case patterns. So, let’s say you have two strings, Greet and Greet2, just like in the example below:
String Greet = "Hello";
String Greet2 = "hello";
boolean isEqual = Greet.equals(Greet2);
System.Out.Println(isEqual);The code above will print a false value. This is because although both Greet and Greet2 have the same character values, there’s a difference in their cases.
To join two strings together, you can make use of the .concat() method. This method will append the new string to the previous string, just like in the example below:
String Greet = "Hello";
String GreetEveryone = Greet.concat("Everyone");As noted earlier, strings in Java are immutable, or can’t be modified. Once you declare a string, you cannot change its value, so understanding proper use at the start is important.
String data objects are created once to optimize memory sharing. If you declare a string and then give it a new value, you create a new string object. This is because. So, if you declare a string with a value, the JVM checks the heap memory to see if there’s an object with the same value and updates it. If not, the JVM creates another string object.
Now the big question is: “How do you work with a string, since they are immutable?” Working with and manipulating the value of a string is easily done by calling a string method. For instance, if you want to add two strings together, you can make use of the concat() method. If you want to remove excessive whitespace, you call the trim() method.
Java application performance monitoring simply refers to the process of analyzing and observing the runtime behavior of Java applications. These tasks help in identifying performance bottlenecks by monitoring various aspects of the application runtime.
There are a number of reasons why applications crash or run slowly. A good and common example is a NullPointerException error. This error happens when your code tries to reference an object without declaring it. This error can be resolved easily if you make use of the Java string method to check if an object is null.
Application monitoring tools, and it’s crucial to understand how they work. One good tool is Stackify, which offers end-user experience monitoring. This feature provides alerts on software performance from the user’s end. Stackify also tracks your application behavior during runtime. It gathers and analyzes data logs to offer possible causes of application crashes. Stackify is also perfect for checking string-related issues like NullPointerException and IndexOutOfBoundsException errors.
Strings are an important concept in every programming language. They’re useful in creating human-computer interaction. In Java, strings are created to be immutable, therefore they cannot be modified. To manipulate string values after declaring them, you have to make use of string methods. In this article, we talked about what string methods are and why they’re important. We also gave some examples of how you can use them in your code.
There are 50 types of Java string methods.
Both == and .equals() methods are used for comparison. But while == is used for comparing the memory address references of two variables, the .equals() method compares the character value of two strings.
An empty string is a string without character values. A null string is a string that has not been declared.
Stackify's APM tools are used by thousands of .NET, Java, PHP, Node.js, Python, & Ruby developers all over the world.
Explore Retrace's product features to learn more.
If you would like to be a guest contributor to the Stackify blog please reach out to [email protected]
