When you think of string, you may see a cat playing around with a ball of yarn. It\u2019s true that a ball or yarn is string, but when programmers use the word string they mean something different.
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In programming, a string is a sequence of one or more characters. Given how important text-based data is to our everyday interactions with computers, it will come at no surprise that the string is a crucial part of programming.
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In this guide, we\u2019re going to discuss how to create a string, how to concatenate a string, and how to store the value of a string in a variable. We\u2019ll walk through a few examples to help guide you along the way.<\/p>\n\n\n\n
A string is used to store text in Java. Whereas the Strings are defined between double quotes. This is unlike languages like Python or JavaScript, which both accept both single and double quotes. Here’s an example of a string in Java: You can print out the contents of a string using the Our code returns: Concatenation, what a long word. It\u2019s definition is quite simple: it means combining two strings to create a new string. You can use the Let\u2019s say that we have two strings: William and Carter. The first string is a forename and the second string is a surname. We could combine them using the Our code outputs: By default, there is no whitespace added between concatenated strings. If we want a space to appear, we’ll need to add it after the name When we run our program, this is returned: How do you calculate the length of a string? What a good question. Luckily for us, we don\u2019t need to write any complex functions to do it. Java already has a built-in function that we can use to calculate the length of a string: We\u2019re going to create a program that calculates the length of the names of two people in a fourth grade class. Create a new Java file and paste the following code into your main class: Let’s run our code:<\/p>\n\n\n\n We\u2019ve defined two variables which store our student’s names: name1 and name2. We\u2019ve then used the Then, we printed out a message informing us of the length of each name.<\/p>\n\n\n\n There may be times when you want to find a string within another string. That’s where the Before we discuss how it works, we\u2019ll have to briefly talk about Here’s a breakdown of the index within the string \u201cWilliam Carter\u201d: Notice that all characters in our string are assigned an index number, including whitespaces. In addition, notice how we start counting from 0. This is because strings are indexed starting at 0. Let\u2019s say we want to find out where the string Our code returns: Carter appears starting at index value 8. Comparing strings comes up all the time in programming. Think about when you enter a password into a login form. What does the application do? It compares the password you have entered with the one the application has stored in its database. Let\u2019s say that we want to write a program that checks whether a user\u2019s password is correct. Open up a new Java file and paste in the following code into your main program: Our code returns: Does the entered password match the saved password? false Our program checks to see whether the two strings we have specified \u2013 Let\u2019s change the value of When we run this code, our program returns: Does the entered password match the saved password? true Both the strings we have specified match, which means that our Strings must be written within double quotes. This sounds like no big deal until you want to include a double quote in your program. This will return an error. The way to resolve this error is to use the backslash (\\) character. This will turn any character that immediately follows the string into a special character. Consider this example: This string will work in our program because we\u2019ve specified a backslash before each of the double quotes in our string. This string returns: Your order for Chocolate Chip Cookie x2 was processed. Now we’ve got another problem: what if you want to use a backslash in your string? To do so, you can write two backslashes side-by-side: This returns the string: There are a number of other special characters that you can use in Java. One of the most useful that you\u2019ll encounter is one called \\n, or new line. This character creates a new line in a string: Our string is equal to: Your order reference is:<\/p>\n\n\n\n The string has been split up onto two lines because we specified a new line character after the char<\/code> data type stores individual characters, strings can hold as many characters as you want. Strings are sequences of bytes.
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<\/p>\n\n\n\n\u201cThis is an example string.\u201d
<\/code><\/p>\n\n\n\nprintln()<\/code> function:
<\/p>\n\n\n\nSystem.out.println(\"This is an example string.\");<\/pre><\/div>\n\n\n\n
This is an example string<\/code>. We\u2019ve constructed a new string. Now that you\u2019re aware of how to declare a string, we can talk about how to work with them in your code. <\/p>\n\n\n\nString Concatenation<\/h2>\n\n\n\n
+<\/code> operator (plus sign) to concatenate two strings.
<\/p>\n\n\n\n+<\/code> operator:
<\/p>\n\n\n\nString fullname = \"William\" + \"Carter\";\nSystem.out.println(fullname);<\/pre><\/div>\n\n\n\n
WilliamCarter<\/code>. Wait, what happened? Why is there not a space between these two words?
<\/p>\n\n\n\nWilliam<\/code>:
<\/p>\n\n\n\nString fullname = \"William \" + \"Carter\";\nSystem.out.println(fullname);<\/pre><\/div>\n\n\n\n
William Carter<\/code>.<\/p>\n\n\n\nCalculating the Length of a String<\/h2>\n\n\n\n
<\/p>\n\n\n\nlength()<\/code>. It’s a convenient name for a method!
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<\/p>\n\n\n\nString name1 = \"William Carter\";\nString name2 = \"Helena Ohara\";\nint name1length = name1.length() - 1;\nint name2length = name2.length() - 1;\nSystem.out.println(name1 + \"'s name is \" + name1length + \" letters long.\");\nSystem.out.println(name2 + \"'s name is \" + name2length + \" letters long.\");<\/pre><\/div>\n\n\n\n
William Carter's name is 13 letters long.\nHelena Ohara's name is 11 letters long.<\/pre><\/div>\n\n\n\n
length()<\/code> method to calculate the length of each of these strings. We subtracted 1 from each of the names\u2019 lengths to account for the space in the middle.
<\/p>\n\n\n\nFind a String within a String<\/h2>\n\n\n\n
indexOf()<\/code> method comes in handy. This method returns the position of the first occurrence of a particular string of text within a string.
<\/p>\n\n\n\nindex<\/code>. In Java, strings are indexed using index numbers. This means that every character in a string is assigned its own number, which we can use to access each item individually.
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<\/p>\n\n\n\nW<\/strong><\/td> i<\/strong><\/td> l<\/strong><\/td> l<\/strong><\/td> i<\/strong><\/td> a<\/strong><\/td> m<\/strong><\/td>
<\/td>C<\/strong><\/td> a<\/strong><\/td> r<\/strong><\/td> t<\/strong><\/td> e<\/strong><\/td> r<\/strong><\/td><\/tr> 0<\/td> 1<\/td> 2<\/td> 3<\/td> 4<\/td> 5<\/td> 6<\/td> 7<\/td> 8<\/td> 9<\/td> 10<\/td> 11<\/td> 12<\/td> 13<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
<\/p>\n\n\n\nCarter<\/code> appears in this string. We could do so using the indexOf()<\/code> method like this:
<\/p>\n\n\n\nString name = \"William Carter\";\nint position = name.indexOf(\"Carter\");\nSystem.out.println(\"Carter appears starting at index value \" + position);<\/pre><\/div>\n\n\n\n
indexOf()<\/code> returns the index position at which a character appears.<\/p>\n\n\n\nCheck Whether Two Strings Are Equal<\/h2>\n\n\n\n
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<\/p>\n\n\n\nString entered_password = \"Test123\";\nString saved_password = \"Test12345\";\nboolean compare_passwords = entered_password.equals(saved_password);\nSystem.out.println(\"Does the entered password match the saved password? \" + compare_passwords);<\/pre><\/div>\n\n\n\n
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<\/p>\n\n\n\nentered_password<\/code> and saved_password<\/code> are equal. We use the equals() <\/code>method to perform this check. This method returns true if the strings are equal; otherwise, it returns false.
<\/p>\n\n\n\nentered_password<\/code> to be equal to saved_password<\/code>:
<\/p>\n\n\n\nString entered_password = \"Test12345\";\nString saved_password = \"Test12345\";\n...<\/pre><\/div>\n\n\n\n
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<\/p>\n\n\n\nequals()<\/code> method evaluates to true.<\/p>\n\n\n\nSpecial Characters<\/h2>\n\n\n\n
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<\/p>\n\n\n\nString statement = \"Your order for \\\"Chocolate Chip Cookie x2\\\" was processed.\";<\/pre><\/div>\n\n\n\n
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<\/p>\n\n\n\nString order_reference = \"Your order reference is 202\\\\303.\"<\/pre><\/div>\n\n\n\n
Your order reference is 202\\303.\"<\/code>
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<\/p>\n\n\n\nString order_reference = \"Your order reference is: \\n 202\\\\303.\"<\/pre><\/div>\n\n\n\n
<\/p>\n\n\n\n202\\303<\/code><\/p>\n\n\n\nis:<\/code> part of our string.<\/p>\n\n\n\n