Things Every Java Programmer Should Know about String. String in Java is very special class and most frequently used class as well. There are lot many things to learn about String in Java than any other class, and having a good knowledge of different String functionalities makes you to use it properly. Given heavy use of Java String in almost any kind of project, it become even more important to know subtle detail about String. Though I have shared lot of String related article already here in Javarevisited, this is an effort to bring some of String feature together. Using Special Characters in Strings. When a string is being created or displayed, its text must be enclosed within double quotation marks to indicate the beginning and end of the string. These quotation marks are not displayed.In this tutorial we will see some important points about Java String, which is worth remembering. You can also refer my earlier post 1. Java String questions to know more about String. Java Programs in the Textbook. UseArgument.java: using a command-line argument: 1.2.1. ArrayStackOfStrings.java: stack of strings (array) 4.3.2: LinkedStackOfStrings.java. Java sample example codes, Java sample programs, Java Example Programs. JAVA EXAMPLE PROGRAMS: Publish Your Article Here Home; Fundamentals; Constructors. Although Java programs are cross-platform or platform independent. Though I tried to cover lot of things, there are definitely few things, which I might have missed; please let me know if you have any question or doubt on java. String functionality and I will try to address them here. Strings are not null terminated in Java. Unlike C and C++, String in Java doesn't terminate with null character. Instead String are Object in Java and backed by character array. You can get the character array used to represent String in Java by calling to. Char. Array() method of java. String class of JDK. Strings are immutable and final in Java. Strings are immutable in Java it means once created you cannot modify content of String. If you modify it by using to. Lower. Case(), to. Upper. Case() or any other method, It always result in new String. Since String is final there is no way anyone can extend String or override any of String functionality. Now if you are puzzled why String is immutable or final in Java. It's worth remembering that equality . By default Java puts all string literal into string pool, but you can also put any string into pool by calling intern() method of java. String class, like string created using new() operator. Use Equals methods for comparing String in Java. The String class represents character strings. All string literals in Java programs, such as 'abc', are implemented as instances of this class. Strings are constant; their values cannot be changed after they are created. Building Java Programs, 3rd edition Lab 3: Strings. Building Java Programs, 3rd edition Lab. Try solving this problem in Practice-It! String class overrides equals method and provides a content equality, which is based on characters, case and order. So if you want to compare two String object, to check whether they are same or not, always use equals() method instead of equality operator. Like in earlier example if we use equals method to compare objects, they will be equal to each other because they all contains same contents. Here is example of comparing String using equals method. String name = . You can useindex. Of()which will return position of character or String, if that exist in current String object or - 1 if character doesn't exists in String. String. match(String regex) is even more powerful, which allows you to search for a regular expression pattern inside String. See here for more examples of String matches() method. Apart from index. Of(), last. Index. Of() and matches(String regex) String also has methods like starts. With() and ends. Width(), which can be used to check an String if it starting or ending with certain character or String. Use Sub. String to get part of String in Java. Java String provides another useful method called substring(), which can be used to get parts of String. Index starts from 0 and goes till String. By the way String. String, including white spaces like tab, space. One point which is worth remembering here is that substring is also backed up by character array, which is used by original String. This can be dangerous if original string object is very large and substring is very small, because even a small fraction can hold reference of complete array and prevents it from being garbage collected even if there is no other reference for that particular String. Read How Substring works in Java for more details. Here is an example of using Sub. String in Java: String str = . It can even used to convert int, char, long or double to convert into String by simply concatenating with empty string . This also brings point of using String. Buffer or String. Builder for manipulating String. Since both represent mutable object they can be used to reduce string garbage created because of temporary String. Read more about String. Buffer vs String. Builder here. 8) Use trim() to remove white spaces from String. String in Java provides trim() method to remove white space from both end of String. If trim() removes white spaces it returns a new String otherwise it returns same String. Along with trim() String also provides replace() and replace. All() method for replacing characters from String. Read more about How to replace String in Java here. Use split() for splitting String using Regular expression. String in Java is feature rich. There are other methods also available related to splitting String, see this Java tutorial to split string for more details. Don't store sensitive data in String. String pose security threat if used for storing sensitive data like passwords, SSN or any other sensitive information. Since String is immutable in Java there is no way you can erase contents of String and since they are kept in String pool (in case of String literal) they stay longer on Java heap ,which exposes risk of being seen by anyone who has access to Java memory, like reading from memory dump. It does not make sense to have a String without knowing what encoding it uses. There is no way to interpret an String if you don't know the encoding it used. You can not assume that . If you have a String, in memory or stored in file, you must know what encoding it is in, or you cannot display it correctly. By default Java uses platform encoding i. I have faced instances where our program fail to interpret Strings from European language e. Thankfully, Java allows you to specify default character encoding for your application using system property file. See here to read more about character encoding in Java. That's all about String in Java. As I have said String is very special in Java, sometime even refer has God class. It has some unique feature like immutability, concatenation support, caching etc, and to become a serious Java programmer, detailed knowledge of String is quite important. Last but not the least don't forget about character encoding while converting a byte array into String in Java. Good knowledge of java. String is must for good Java developers.
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