org.scijava.parse.SubSequence Maven / Gradle / Ivy
/*
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* Parsington: the SciJava mathematical expression parser.
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package org.scijava.parse;
/**
* A {@link CharSequence} which is a by-reference subsequence of another
* {@link CharSequence}. This is particularly useful for
* {@link java.util.regex.Pattern regex} matching without excessive string
* copying.
*
* Surprisingly, core Java does not seem to have this capability (apart from
* {@link javax.swing.text.Segment}, which seems misplaced in the Swing
* library); all of {@link String#subSequence}, {@link StringBuffer#subSequence}
* and {@link StringBuilder#subSequence} internally copy the requested string
* segment.
*
*
* @author Curtis Rueden
*/
public class SubSequence implements CharSequence {
private final CharSequence seq;
private final int offset;
private final int length;
public SubSequence(final CharSequence seq, final int offset) {
this(seq, offset, seq.length() - offset);
}
private static void outOfBounds(final String message) {
throw new IndexOutOfBoundsException(message);
}
public SubSequence(final CharSequence seq, final int offset, final int length)
{
if (offset < 0) outOfBounds("Offset " + offset + " < 0");
if (offset > seq.length()) {
outOfBounds("Offset " + offset + " > " + seq.length());
}
if (length < 0) outOfBounds("Length " + length + " < 0");
if (offset + length > seq.length()) {
outOfBounds("Offset " + offset + " + length " + length + " > " +
seq.length());
}
this.seq = seq;
this.offset = offset;
this.length = length;
}
// -- CharSequence methods --
@Override
public int length() {
return length;
}
@Override
public char charAt(final int index) {
return seq.charAt(offset + index);
}
@Override
public SubSequence subSequence(final int start, final int end) {
return new SubSequence(seq, offset + start, end - start);
}
// -- Object methods --
@Override
public String toString() {
return seq.subSequence(offset, offset + length).toString();
}
}