org.incava.ijdk.util

Class Index

java.lang.Object

org.incava.ijdk.util.Index

public class Index
extends java.lang.Object

Wraps index calculations similar to Ruby, where index -2 means the next-to-last element in a list.

Constructor Summary

Constructors

Constructor and Description
Index()

Method Summary

Modifier and Type	Method and Description
static java.lang.Integer	getIndex(java.lang.Integer size, java.lang.Integer index) Converts index, which can be positive or negative, to an offset within the given size, representing the length of a list (including strings).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Index

public Index()

Method Detail

getIndex

public static java.lang.Integer getIndex(java.lang.Integer size,
                                         java.lang.Integer index)

Converts index, which can be positive or negative, to an offset within the given size, representing the length of a list (including strings). A negative index will result in the distance from the end of the list, with index -1 meaning the last element in the list, -2 the second to last, etc. Returns null if:

• the resulting index is out of range (< 0 or ≥ size)
• size is 0 or null
• the resulting value is out of range (such as getIndex(2, -3) or getIndex(1, 2))

Examples:

     getIndex(null, 0);  // == null
     getIndex(0, 0);     // == null
     getIndex(4, 0);     // == 0
     getIndex(4, 1);     // == 1
     getIndex(4, 3);     // == 3
     getIndex(4, 4);     // == null
     getIndex(4, -1);    // == 3
     getIndex(4, -2);    // == 2
     getIndex(4, -3);    // == 1
     getIndex(4, -4);    // == 0
     getIndex(4, -5);    // == null
 

Parameters:

size - the size into which the index is applied

index - the index within the size

Returns:

the offset value for the index for the given size