日撸java_day19

第 19 天: 字符串匹配

19.1 String 是 Java 常用的类, 这里重新实现下部分功能.
19.2 转义符 , 有了它才能正常打印引号.
19.3 简单的越界检查.

package datastructures;

/**
 * ClassName: MyString
 * Package: datastructures
 * Description: My string. String is a class provided by the language, so I use another name.
 * It is essentially a sequential list with char type elements.
 *
 * @Author: luv_x_c
 * @Create: 2023/4/23 9:33
 */
public class MyString {
    /**
     * The maximal length.
     */
    public static final int MAX_LENGTH = 10;

    /**
     * The actual length.
     */
    int length;

    /**
     * The data.
     */
    char[] data;

    /**
     * Construct an empty char array.
     */
    public MyString() {
        length = 0;
        data = new char[MAX_LENGTH];
    }// Of the first constructor

    /**
     * Construct using a system defined string.
     *
     * @param paraString The given string. Its length should not exceed MAX_LENGTH - 1.
     */
    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

    /**
     * Overrides the method claimed in Object, the superclass of any class.
     *
     * @return A String.
     */
    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 paraMyString 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++) {
            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 paraStartPosition The start position in the original string.
     * @param paraLength        The length of the new string.
     * @return Get a substring.
     */
    public MyString substring(int paraStartPosition, int paraLength) {
        if (paraStartPosition + paraLength > length) {
            System.out.println("The bound is exceed. ");
            return null;
        }// Of if

        MyString resultString = new MyString();
        resultString.length = paraLength;
        for (int i = 0; i < paraLength; i++) {
            resultString.data[i] = data[paraStartPosition + 1];
        }// Of for i

        return resultString;
    }//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);

        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