第 19 天: 字符串匹配

字符串匹配原理简单，但是对于代码有一点疑问，主要是基础的不牢固，对语法的理解不太行，核心思想没有什么问题。先上今天打的代码。

package day17;

public class MyString {
	public static final int MAX_LENGTH = 10;
	char[] data;
	int length;

	public MyString() {
		length = 0;
		data = new char[MAX_LENGTH];
	}// Of the first constructor

	public MyString(String paraString) {
		data = new char[MAX_LENGTH];
		length = paraString.length();
		// Copy data.
		for (int i = 0; i < length; i++) {
			data[i] = paraString.charAt(i);
		} // Of for i
	}// Of the second constructor

	public String toString() {
		String resultString = "";
		for (int i = 0; i < length; i++) {
			resultString += data[i];
		} // Of for i

		return resultString;

	}// Of toString

	/**
	 *********************
	 * Locate the position of a substring.
	 * 
	 * @param paraString The given substring.
	 * @return The first position. -1 for no matching.
	 *********************
	 */

	public int locate(MyString paraMyString) {
		boolean tempMatch = false;
		for (int i = 0; i < length - paraMyString.length + 1; i++) {
			// Initialize.
			tempMatch = true;
			for (int j = 0; j < paraMyString.length; j++) {
				if (data[i + j] != paraMyString.data[j]) {
					tempMatch = false;
					break;
				} // Of if
			} // Of for j

			if (tempMatch) {
				return i;
			} // Of if
		} // Of for i
		return -1;
	}// Of locate

	/**
	 *********************
	 * Get a substring
	 * 
	 * @param paraString        The given substring.
	 * @param paraStartPosition The start position in the original string.
	 * @param paraLength        The length of the new string.
	 * @return The first position. -1 for no matching.
	 *********************
	 */
	public MyString substring(int paraStartPosition, int paraLength) {
		if (paraStartPosition + paraLength > length) {
			System.out.println("The bound is exceeded.");
			return null;
		} // Of if

		MyString resultMyString = new MyString();
		resultMyString.length = paraLength;
		for (int i = 0; i < paraLength; i++) {
			resultMyString.data[i] = data[paraStartPosition + i];
		} // Of for i

		return resultMyString;
	}// Of substring

	/**
	 *********************
	 * The entrance of the program.
	 * 
	 * @param args Not used now.
	 *********************
	 */
	public static void main(String args[]) {
		MyString tempFirstString = new MyString("I like ik.");
		MyString tempSecondString = new MyString("ik");
		int tempPosition = tempFirstString.locate(tempSecondString);
		System.out.println(
				"The position of \"" + tempSecondString + "\" in \"" + tempFirstString + "\" is: " + tempPosition);
		System.out.println(tempSecondString.length);
		MyString tempThirdString = new MyString("ki");
		tempPosition = tempFirstString.locate(tempThirdString);
		System.out.println(
				"The position of \"" + tempThirdString + "\" in \"" + tempFirstString + "\" is: " + tempPosition);

		tempThirdString = tempFirstString.substring(1, 2);
		System.out.println("The substring is: \"" + tempThirdString + "\"");

		tempThirdString = tempFirstString.substring(5, 5);
		System.out.println("The substring is: \"" + tempThirdString + "\"");

		tempThirdString = tempFirstString.substring(5, 6);
		System.out.println("The substring is: \"" + tempThirdString + "\"");
	}// Of main

	
	
}// Of class MyString

当时对于locate方法的外层for循环条件不理解，觉得这个length并没有指明到底是哪个length，然后反复看了下第二个构造器和主方法的调用，理解了这个length就是你最开始new的那个MyString的长度。然后又觉得不对了，觉得不该+1，结果自己一把字符串假设出来模拟发现需要+1。

然后就是入口的输出内容，对于转义符这里做一个总结：

 总的来说，对于构造器的理解不够，还有些语法，书写习惯有问题，但是对于代码的核心思想还是掌握了，需要更多书写。