Tampilkan postingan dengan label Java String. Tampilkan semua postingan
Tampilkan postingan dengan label Java String. Tampilkan semua postingan

Selasa, 24 Januari 2017

You can use the split() method of String class from JDK to split a String based on a delimiter e.g. splitting a comma separated String on a comma, breaking a pipe delimited String on a pipe or splitting a pipe delimited String on a pipe. It's very similar to earlier examples where you have learned how to split String in Java. The only point which is important to remember is little bit knowledge of regular expression, especially when the delimiter is also a special character in regular expression e.g. pipe (|) or dot (.), as seen in how to split String by dot in Java. In those cases, you need to escape these characters e.g. instead of |, you need to pass \\| to the split method.
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Kamis, 19 Januari 2017

You can replace all occurrence of a single character, or a substring of a given String in Java using the replaceAll() method of java.lang.String class. This method also allows you to specify the target substring using the regular expression, which means you can use this to remove all white space from String. The replaceAll() function is very useful, versatile and powerful method and as a Java developer, you must know about it. Even though Java provides separate methods for replacing characters and replacing substring, you can do all that just by using this single method. The replaceAll() method replaces each substring of this string (the String on which it is called) that matches the given regular expression with the given replacement. It internally uses classes like Pattern and Matcher from java.util.regex package for searching and replacing matching characters or substring.
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Kamis, 13 Oktober 2016

You can use contains(), indexOf() and lastIndexOf() method to check if one String contains another String in Java or not. If a String contains another String then it's known as a substring. The indexOf() method accept a String and return starting position of the string if it exists, otherwise it will return -1. For example "fastfood".indexOf("food") will return 4 but "fastfood".indexOf("Pizza") will return -1. This is the easiest way to test if one String contains another substring or not. The second method is lastIndexOf() which is similar to indexOf() but start the search from the tail, but it will also return -1 if substring not found in the String or the last position of the substring, which could be anything between 0 and length -1.
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Selasa, 11 Oktober 2016

In day-to-day programming, you often need to check if a given String is numeric or not. It's also a good interview question but that's a separate topic of discussion. Even though you can use a Regular expression to check if given String is empty or not, as shown here, they are not full proof to handle all kinds of scenarios, which common third party library like Apache commons lang will handle e.g. hexadecimal and octal String. Hence, In Java application, the simplest way to determine if a String is a number or not is by using Apache Commons lang's isNumber() method, which checks whether the String a valid number in Java or not. Valid numbers include hexadecimal marked with the 0x or 0X qualifier, octal numbers, scientific notation and numbers marked with a type qualifier (e.g. 123L). Non-hexadecimal strings beginning with a leading zero are treated as octal values. Thus the string 09 will return false since 9 is not a valid octal value. However, numbers beginning with 0. are treated as decimal.null and empty/blank String will return false.
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Sabtu, 08 Oktober 2016

You can split a String by whitespaces or tabs in Java by using the split() method of java.lang.String class. This method accepts a regular expression and you can pass a regex matching with whitespace to split the String where words are separated by spaces. Though this is not as straightforward as it seems, especially if you are not coding in Java regularly. Input String may contain leading and trailing spaces, it may contain multiple white spaces between words and words may also be separated by tabs. Your solution needs to take care of all these conditions if you just wants words and no empty String. In this article, I am going to show you a couple of examples to demonstrate how you can split String in Java by space. By splitting I mean getting individual words as String array or ArrayList of String, whatever you need.
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Jumat, 15 Juli 2016

String pool in Java is a pool of String literals and interned Strings in JVM for efficient use of String object. Since String is immutable in Java, it makes sense to cache and shares them in JVM. The String pool has gone through an important change in Java 7 release when it was relocated from PermGen space to heap space. Till Java 1.6, interned String and literals are stored in the PermGen space of JVM memory, which was a fixed size area for storing class metadata. The biggest issue of having String pool in PermGen is the small and fixed size of PermGen space. In some JVM it ranges from 32M to 96M, which is quite small for a large program. Since String is extensively used in both small and large Java application, Java designers thought String pool is the best way optimize the use of String object in Java.
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