Added a StringLineIterator that helps read a string line-by-line while

maintaing the start/end index positions and the current line number

.gitignore

@@ -39,3 +39,4 @@ target/*
 .settings/*
 /target
 com/sangupta/jerry/*
+/target/

src/main/java/com/sangupta/jerry/io/StringLineIterator.java

@@ -0,0 +1,178 @@
+/**
+ *
+ * jerry - Common Java Functionality
+ * Copyright (c) 2012-2014, Sandeep Gupta
+ * 
+ * http://sangupta.com/projects/jerry
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ * 		http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * 
+ */
+
+package com.sangupta.jerry.io;
+
+import java.util.Arrays;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+
+/**
+ * A simple iterator that reads a {@link String} line-by-line and
+ * also maintains the line number, the starting and ending index positions
+ * of the current read line.
+ * 
+ * This may be useful when parsing a source file where positions need
+ * to be maintained.
+ * 
+ * @author sangupta
+ *
+ */
+public class StringLineIterator implements Iterator<String> {
+
+	/**
+	 * The character array backing this iterator.
+	 */
+	private final char[] chars;
+
+	/**
+	 * The length of the string
+	 */
+	private final int length;
+
+	/**
+	 * Holds the current line number
+	 */
+	private int lineNumber = -1;
+
+	/**
+	 * Holds the beginning of the current line
+	 */
+	private int lineBegin = -1;
+
+	/**
+	 * Holds the ending of current line
+	 */
+	private int lineEnd = -1;
+
+	/**
+	 * Current read position in array
+	 */
+	private int current;
+
+	/**
+	 * Create a new instance of the {@link StringLineIterator}.
+	 * 
+	 * @param input
+	 */
+	public StringLineIterator(String input) {
+		this.chars = input.toCharArray();
+		this.length = input.length();
+	}
+
+	@Override
+	public boolean hasNext() {
+		if(this.current >= this.length) {
+			return false;
+		}
+
+		return true;
+	}
+
+	@Override
+	public String next() {
+		if(!hasNext()) {
+			throw new NoSuchElementException("No more lines");
+		}
+
+		if(this.lineNumber < 0) {
+			this.lineNumber = 0;
+		}
+
+		for(int index = this.current; index < this.length; index++) {
+			char c = chars[index];
+			if(c == '\n') {
+				this.lineNumber++;
+				this.lineBegin = this.current;
+				this.lineEnd = index;
+				this.current = index + 1;
+
+				return new String(Arrays.copyOfRange(this.chars, this.lineBegin, this.lineEnd));
+			}
+
+			if(c == '\r') {
+				this.lineNumber++;
+				this.lineBegin = this.current;
+				this.lineEnd = index;
+				this.current = index + 1;
+				if(chars[index + 1] == '\n') {
+					this.current++;
+				}
+
+				return new String(Arrays.copyOfRange(this.chars, this.lineBegin, this.lineEnd));
+			}
+		}
+
+		// we are till the end of file
+		this.lineNumber++;
+		this.lineBegin = this.current;
+		this.lineEnd = this.length;
+		this.current = this.length;
+		return new String(Arrays.copyOfRange(this.chars, this.lineBegin, this.length));
+	}
+
+	/**
+	 * Return the current line number.
+	 * 
+	 * @return
+	 */
+	public int getLineNumber() {
+		return this.lineNumber;
+	}
+
+	/**
+	 * Return the index position at which the current line starts.
+	 * 
+	 * @return
+	 */
+	public int getLineBegin() {
+		return this.lineBegin;
+	}
+
+	/**
+	 * Return the index position at which the current line ends.
+	 * 
+	 * @return
+	 */
+	public int getLineEnd() {
+		return this.lineEnd;
+	}
+
+	/**
+	 * Return the index position at which the next read for the line will
+	 * occur.
+	 * 
+	 * @return
+	 */
+	public int getNextLineBegin() {
+		if(this.current >= this.length) {
+			return -1;
+		}
+
+		return this.current;
+	}
+
+	@Override
+	public void remove() {
+		throw new UnsupportedOperationException("Remove unsupported on LineIterator");
+	}
+
+}

src/test/java/com/sangupta/jerry/io/StringLineIteratorTest.java

@@ -0,0 +1,209 @@
+/**
+ *
+ * jerry - Common Java Functionality
+ * Copyright (c) 2012-2014, Sandeep Gupta
+ * 
+ * http://sangupta.com/projects/jerry
+ * 
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * 
+ * 		http://www.apache.org/licenses/LICENSE-2.0
+ * 
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * 
+ */
+
+package com.sangupta.jerry.io;
+
+import junit.framework.Assert;
+
+import org.junit.Test;
+
+/**
+ * Unit tests for {@link StringLineIterator}.
+ * 
+ * @author sangupta
+ *
+ */
+public class StringLineIteratorTest {
+
+	@Test
+	public void testNewLines() {
+		String input = "\n\n\n\n";
+		StringLineIterator it = new StringLineIterator(input);
+
+		Assert.assertEquals(-1, it.getLineNumber());
+		Assert.assertEquals(-1, it.getLineBegin());
+		Assert.assertEquals(-1, it.getLineEnd());
+
+		// first read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("", it.next());
+		Assert.assertEquals(1, it.getLineNumber());
+
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("", it.next());
+		Assert.assertEquals(2, it.getLineNumber());
+
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("", it.next());
+		Assert.assertEquals(3, it.getLineNumber());
+
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("", it.next());
+		Assert.assertEquals(4, it.getLineNumber());
+
+		Assert.assertFalse(it.hasNext());
+	}
+
+	@Test
+	public void testStringLineIterator1() {
+		String input = "one\ntwo\nthree\nfour";
+		StringLineIterator it = new StringLineIterator(input);
+
+		Assert.assertEquals(-1, it.getLineNumber());
+		Assert.assertEquals(-1, it.getLineBegin());
+		Assert.assertEquals(-1, it.getLineEnd());
+
+		// first read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("one", it.next());
+		Assert.assertEquals(1, it.getLineNumber());
+		Assert.assertEquals("one", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// second read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("two", it.next());
+		Assert.assertEquals(2, it.getLineNumber());
+		Assert.assertEquals("two", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// third read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("three", it.next());
+		Assert.assertEquals(3, it.getLineNumber());
+		Assert.assertEquals("three", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// fourth read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("four", it.next());
+		Assert.assertEquals(4, it.getLineNumber());
+		Assert.assertEquals("four", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		Assert.assertFalse(it.hasNext());
+	}
+
+	@Test
+	public void testStringLineIterator2() {
+		String input = "one\rtwo\rthree\rfour";
+		StringLineIterator it = new StringLineIterator(input);
+
+		Assert.assertEquals(-1, it.getLineNumber());
+		Assert.assertEquals(-1, it.getLineBegin());
+		Assert.assertEquals(-1, it.getLineEnd());
+
+		// first read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("one", it.next());
+		Assert.assertEquals(1, it.getLineNumber());
+		Assert.assertEquals("one", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// second read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("two", it.next());
+		Assert.assertEquals(2, it.getLineNumber());
+		Assert.assertEquals("two", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// third read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("three", it.next());
+		Assert.assertEquals(3, it.getLineNumber());
+		Assert.assertEquals("three", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// fourth read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("four", it.next());
+		Assert.assertEquals(4, it.getLineNumber());
+		Assert.assertEquals("four", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		Assert.assertFalse(it.hasNext());
+	}
+
+	@Test
+	public void testStringLineIterator3() {
+		String input = "one\r\ntwo\r\nthree\r\nfour";
+		StringLineIterator it = new StringLineIterator(input);
+
+		Assert.assertEquals(-1, it.getLineNumber());
+		Assert.assertEquals(-1, it.getLineBegin());
+		Assert.assertEquals(-1, it.getLineEnd());
+
+		// first read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("one", it.next());
+		Assert.assertEquals(1, it.getLineNumber());
+		Assert.assertEquals("one", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// second read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("two", it.next());
+		Assert.assertEquals(2, it.getLineNumber());
+		Assert.assertEquals("two", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// third read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("three", it.next());
+		Assert.assertEquals(3, it.getLineNumber());
+		Assert.assertEquals("three", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// fourth read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("four", it.next());
+		Assert.assertEquals(4, it.getLineNumber());
+		Assert.assertEquals("four", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		Assert.assertFalse(it.hasNext());
+	}
+
+	@Test
+	public void testStringLineIterator4() {
+		String input = "one\r\ntwo\nthree\r\nfour";
+		StringLineIterator it = new StringLineIterator(input);
+
+		Assert.assertEquals(-1, it.getLineNumber());
+		Assert.assertEquals(-1, it.getLineBegin());
+		Assert.assertEquals(-1, it.getLineEnd());
+
+		// first read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("one", it.next());
+		Assert.assertEquals(1, it.getLineNumber());
+		Assert.assertEquals("one", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// second read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("two", it.next());
+		Assert.assertEquals(2, it.getLineNumber());
+		Assert.assertEquals("two", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// third read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("three", it.next());
+		Assert.assertEquals(3, it.getLineNumber());
+		Assert.assertEquals("three", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		// fourth read
+		Assert.assertTrue(it.hasNext());
+		Assert.assertEquals("four", it.next());
+		Assert.assertEquals(4, it.getLineNumber());
+		Assert.assertEquals("four", input.substring(it.getLineBegin(), it.getLineEnd()));
+
+		Assert.assertFalse(it.hasNext());
+	}
+
+}