Strings in Java

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String (computer science)
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This article is about the data type. For other uses, see String.

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Diagram of String data in computing. Shows the sentence "This is a string!" with each letter in a separate box. The word "String" is above, referring to the entire sentence. The label "Character" is below and points to individual boxes.
Strings are often made up of characters. They are useful for storing human-readable data, like sentences, or lists of alphabetical data, like the nucleic acid sequences of DNA.
In computer programming, a string is traditionally a sequence of characters, either as a literal constant or as some kind of variable. The latter may allow its elements to be mutated and the length changed, or it may be fixed (after creation). A string is generally considered as a data type and is often implemented as an array data structure of bytes (or words) that stores a sequence of elements, typically characters, using some character encoding. String may also denote more general arrays or other sequence (or list) data types and structures.

Depending on the programming language and precise data type used, a variable declared to be a string may either cause storage in memory to be statically allocated for a predetermined maximum length or employ dynamic allocation to allow it to hold a variable number of elements.

When a string appears literally in source code, it is known as a string literal or an anonymous string.[1]

In formal languages, which are used in mathematical logic and theoretical computer science, a string is a finite sequence of symbols that are chosen from a set called an alphabet.


Contents
1 String datatypes
1.1 String length
1.2 Character encoding
1.3 Implementations
1.4 Representations
1.4.1 Null-terminated
1.4.2 Byte- and bit-terminated
1.4.3 Length-prefixed
1.4.4 Strings as records
1.4.5 Other representations
1.5 Security concerns
2 Literal strings
3 Non-text strings
4 String processing algorithms
5 Character string-oriented languages and utilities
6 Character string functions
7 Formal theory
7.1 Concatenation and substrings
7.2 Prefixes and suffixes
7.3 Reversal
7.4 Rotations
7.5 Lexicographical ordering
7.6 String operations
7.7 Topology
8 See also
9 References