Constant String

Constant String is a library for doing constant time string manipulation in Java.

CString cs = CString.create("foo")
    .concat(CString.create("bar"))
    .substring(3)
    .concat(CString.create("bara"))
    .delete(3,7)
    .insert(0, CString.create("foo"));

cs.toString(); // foobar

Perhaps not the most useful thing in everyday programming, but still a fun exercise to implement.

Using

The artifacts are published on Maven Central, so trying it out is as simple as adding the dependency to you pom.xml or gradle file.

<dependency>
  <groupId>us.klette</groupId>
  <artifactId>constantstring</artifactId>
  <version>2.0</version>
</dependency>

API

Constant String exposes a simple API via the CString-interface. The static method CString.create(...) allows you to quickly create a new instance of a (hidden) implementation of the interface. Some of the operations are similar to the ones found on the built-in Java String class, such as the substring method. On these we try hard to map the arguments and functionality as close as possible.

Operations

The following operations are supported by the API.

toString()

The toString()-method evaluates the graph of operations, and returns the final result as a String. This is done in a non-constant time.

Create

Create a new CString instance from a String.

Example

CString myStr = CString.create("The start of my text goes like this..")

Substring

Extracts a part of a String, either only by start index to the end of the string, or by a start index and an end index.

Examples

myStr.substring(4).toString() // "start of my text goes like this.."
myStr.substring(4,8).toString() // "start"

Concat

Appends a String at the end of the current value.

Example

CString.create("foo")
       .concat(CString.create("ba"))
       .concat("r")
       .toString() // "foobar" 

Delete

Delete part of a string specified by a start index and an end index.

Example

CString.create("foobar").delete(3,6).toString() // "foo"

Insert

Inserts a String at a given index.

Example

CString.create("foar").insert("o",2).insert(CString.create("b"), 3).toString() // "foobar"