This is a utility to convert a byte array to hex string, and to convert a hex string back to the original. To convert a String to hex, you must call String.getBytes() first. The utility does not pretend to know your string encoding. public class StringHexUtil { public static ... This also works: String binaryToHex(byte[] data) { StringBui...

This is an HTML image tag filter using Java regex. It takes a string, finds the img tags, replaces the src attribute with one provided by the filter, then adds a class name to the class attribute. import java.util.regex.*; import java.io.*; ... Test file: <div id="HTML snippet"> <img src="img/big/txt-m...

Some methods to search for a substring within a string: To know that a substring indeed exists within a string: boolean found = wholeString.contains(substring); To find where the substring is contained: int index = wholeString.indexOf(substring); If the substring is regex: boolean match = wholeString.matches(".*" + substri... Case insensitive match: convert both whole string and substring to lowercase, then compare. Or, use case insensitive flag for regex. Test code: import java.util.regex.*; public class Stri...

This is not to make the size of the array smaller, but to remove the leading and trailing spaces in each element. This works: String[] a = { " 1 ", " 2 " }; for (int i = 0; ... This does not work: for (String s: a) { s = s.trim(); }

You can iterate through an array of String like this: String[] a = { "one", "two", "three" }; for (in... or like this: for (String s: a) { System.out.println(s); ... For a string Collection , iterate like this: Collection<String> c = Arrays.asList("one", "two",... or like this: Collection<String> c = Arrays.asList("one", "two",...

The one argument version of String.split omits trailing empty strings. To get all parts, including trailing empty strings, you need to use the two argument version with a negative limit : public class TestStringSplit { public stati... Output: Length of array: 8 Part[0]: '1' Part[1]: '2'...

From the Java Language Specification : Because some type information is erased during compilation, not all types are available at run time. Types that are completely available at run time are known as reifiable types . A type is reifiable if and only if one of the following holds: It refers to a non-generic type declaration. It is a parameterized type in which all type arguments are unbounded wildcards. It is a raw type. It is a primitive type. It is an array type whose component type is reifiable. For example: int is a reifiable type (primitive type) List is a reifiable type (raw type) List<?> is a reifiable type (parameterized type with unbound wildcards) List<String> is not a reifiable type (generic type) Class<?> is...

There's no such thing as an immutable byte array in Java. What we are trying to achieve here is to protect the byte array inside the object from which it is being returned. We want to caller to have the contents of the byte array, but not be able to change the contents inside the object. The trick is to return a copy instead of the internal reference: public class ReturnByteArray { public stati...

Demo code for CSV parsing with OpenCSV . Java code: import java.io.*; import au.com.bytecode.opencs... Test with a simple CSV file: psmith01,CLASS2B,Peter Smith 1,YEAR2,1,N,ADVANCED,... The parser worked correctly: Line 1 has 11 values: |psmith01| |CLASS2B|... Test with a more complicated CSV file: "psmith01 abc", "CLASS2B " , " Peter... Result: Line 1 has 4 values: |psmith01 abc| |CLASS... The parser: Escaped quote and backslash correctly Ignored spaces before the quotation mark - sometimes (see below) Counted spaces after the right quotation mark till the comma as content, including the right quotation mark (bug). Ignored improperly quoted item - silently (third line) Indeed, the OpenCSV parser has a problem with spaces: Input: "Smith, Jack", "210-345-8888" "Smith, J... Result: Line 1 has 2 values: | Smith, Jack| |210-3......

Demo code for CSV parsing with Skife CSV . Java code: import java.io.*; import java.util.*; import... Test with a simple CSV file: psmith01,CLASS2B,Peter Smith 1,YEAR2,1,N,ADVANCED,... The parser worked correctly: Line 1 has 11 values: |psmith01| |CLASS2B|... Test with a more complicated CSV file: "psmith01 abc", "CLASS2B " , " Peter... Result: Line 1 has 4 values: |psmith01 abc| | CLAS... The parser worked correctly. But notice that it counts the spaces outside of the quotes significant, and doing so consistently. One more test for spaces: "Smith, Jack" , "210-345-8888" "Smith, Jack"... Result: Line 1 has 2 values: | Smith, Jack | | 210... Add a new line in item two: "One", "Two ", "Three" Result: Line 1 has 2 values: |One| | Two| L...