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:
转义字符 | 意义 | ASCII码值(十进制) |
\b | 退格(BS) ,将当前位置移到前一列 | 008 |
\f | 换页(FF),将当前位置移到下页开头 | 012 |
\n | 换行(LF) ,将当前位置移到下一行开头 | 010 |
\r | 回车(CR) ,将当前位置移到本行开头 | 013 |
\t | 水平制表(HT) (跳到下一个TAB位置) | 009 |
\v | 垂直制表(VT) | 011 |
\\ | 代表一个反斜线字符''\' | 092 |
\' | 代表一个单引号(撇号)字符 | 039 |
\" | 代表一个双引号字符 | 034 |
\0 | 空字符(NULL) | 000 |
\ddd | 1到3位八进制数所代表的任意字符 | 三位八进制 |
\uhhhh | 1到2位十六进制所代表的任意字符 | 二位十六进制 |
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。