Wrapper for arrays of ordered strings. This verifies the arrays and supports efficient lookups.
/**
* Wrapper for arrays of ordered strings. This verifies the arrays and supports
* efficient lookups.
*
* @author Dennis M. Sosnoski
*/
public class StringArray
{
/** Ordered array of strings. */
private final String[] m_list;
/**
* Constructor from array of values. This checks the array values to make
* sure they're ordered and unique, and if they're not throws an exception.
* Once the array has been passed to this constructor it must not be
* modified by outside code.
*
* @param list array of values
*/
public StringArray(String[] list) {
validateArray(list);
m_list = list;
}
/**
* Constructor from array of values to be added to base instance. This
* merges the array values, making sure they're ordered and unique, and if
* they're not throws an exception.
*
* @param list array of values
* @param base base instance
*/
public StringArray(String[] list, StringArray base) {
validateArray(list);
m_list = mergeArrays(list, base.m_list);
}
/**
* Constructor from pair of base instances. This merges the values, making
* sure they're unique, and if they're not throws an exception.
*
* @param array1 first base array
* @param array2 second base array
*/
public StringArray(StringArray array1, StringArray array2) {
m_list = mergeArrays(array1.m_list, array2.m_list);
}
/**
* Constructor from array of values to be added to pair of base instances.
* This merges the array values, making sure they're ordered and unique, and
* if they're not throws an exception.
*
* @param list array of values
* @param array1 first base array
* @param array2 second base array
*/
public StringArray(String[] list, StringArray array1, StringArray array2) {
validateArray(list);
m_list = mergeArrays(list, mergeArrays(array1.m_list, array2.m_list));
}
/**
* Constructor from array of values to be added to three base instances.
* This merges the array values, making sure they're ordered and unique, and
* if they're not throws an exception.
*
* @param list array of values
* @param array1 first base array
* @param array2 second base array
* @param array3 third base array
*/
public StringArray(String[] list, StringArray array1, StringArray array2,
StringArray array3) {
validateArray(list);
m_list = mergeArrays(list, mergeArrays(array1.m_list,
mergeArrays(array2.m_list, array3.m_list)));
}
/**
* Constructor from array of values to be added to four base instances.
* This merges the array values, making sure they're ordered and unique, and
* if they're not throws an exception.
*
* @param list array of values
* @param array1 first base array
* @param array2 second base array
* @param array3 third base array
* @param array4 fourth base array
*/
public StringArray(String[] list, StringArray array1, StringArray array2,
StringArray array3, StringArray array4) {
validateArray(list);
m_list = mergeArrays(list, mergeArrays(array1.m_list,
mergeArrays(array2.m_list,
mergeArrays(array3.m_list, array4.m_list))));
}
/**
* Merge a pair of ordered arrays into a single array. The two source arrays
* must not contain any values in common.
*
* @param list1 first ordered array
* @param list2 second ordered array
* @return merged array
*/
private String[] mergeArrays(String[] list1, String[] list2) {
String[] merge = new String[list1.length + list2.length];
int fill = 0;
int i = 0;
int j = 0;
while (i < list1.length && j < list2.length) {
int diff = list2[j].compareTo(list1[i]);
if (diff > 0) {
merge[fill++] = list1[i++];
} else if (diff < 0) {
merge[fill++] = list2[j++];
} else {
throw new IllegalArgumentException
("Repeated value not allowed: \"" + list1[i] + '"');
}
}
if (i < list1.length) {
System.arraycopy(list1, i, merge, fill, list1.length-i);
}
if (j < list2.length) {
System.arraycopy(list2, j, merge, fill, list2.length-j);
}
return merge;
}
/**
* Make sure passed-in array contains values that are in order and without
* duplicate values.
*
* @param list
*/
private void validateArray(String[] list) {
if (list.length > 0) {
String last = list[0];
int index = 0;
while (++index < list.length) {
String comp = list[index];
int diff = last.compareTo(comp);
if (diff > 0) {
throw new IllegalArgumentException
("Array values are not ordered");
} else if (diff < 0) {
last = comp;
} else {
throw new IllegalArgumentException
("Duplicate values in array");
}
}
}
}
/**
* Get string at a particular index in the list.
*
* @param index list index to be returned
* @return string at that index position
*/
public String get(int index) {
return m_list[index];
}
/**
* Find index of a particular string in the array. This does
* a binary search through the array values, using a pair of
* index bounds to track the subarray of possible matches at
* each iteration.
*
* @param value string to be found in list
* @return index of string in array, or <code>-1</code> if
* not present
*/
public int indexOf(String value) {
int base = 0;
int limit = m_list.length - 1;
while (base <= limit) {
int cur = (base + limit) >> 1;
int diff = value.compareTo(m_list[cur]);
if (diff < 0) {
limit = cur - 1;
} else if (diff > 0) {
base = cur + 1;
} else {
return cur;
}
}
return -1;
}
/**
* Get number of values in array
*
* @return number of values in array
*/
public int size() {
return m_list.length;
}
}
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