Hints and Tips You can use and to compare char values whic

Hints and Tips

You can use < and > to compare char values, which have relatively straightforward meanings for letters and numbers. You can look up an ASCII table (just use Google) if you want to see what the underlying values are.

Remember to use .equals to compare String values, not ==.

Double-check indices and documentation when using charAt() and substring() on Strings, to avoid out-of-bounds indexing.

Please complete the code below. Thanks

interface StringMatcher {
public int match(String s, int start);
}

class SCM implements StringMatcher {
private final char c;
public SCM(char c) {
this.c = c;
}
public int match(String s, int start) {
if(s.length() <= start) { return -1; }
if(s.charAt(start) == this.c) { return start + 1; }
return -1;
}
}

class RCM implements StringMatcher {
private final char from, to;
public RCM(char from, char to) { this.from = from; this.to = to; }
public int match(String s, int start) {
return -1;
}
}

class STR implements StringMatcher {
private final String str;
public STR(String str) { this.str = str; }
public int match(String s, int start) {
return -1;
}
}

class SEQ implements StringMatcher {
private final StringMatcher first, second;
public SEQ(StringMatcher first, StringMatcher second) {
this.first = first;
this.second = second;
}
public int match(String s, int start) {
return -1;
}
}

public class Main {
public static void main(String[] args) {
  
StringMatcher ti = new STR(\"testinput\");
StringMatcher oneToSix = new RCM(\'1\', \'6\');
StringMatcher dotTxt = new STR(\".txt\");
  
// Write some small printout tests of these individually

StringMatcher s = new SEQ(ti, new SEQ(oneToSix, dotTxt));
int m = s.match(\"testinput1.txt\", 0);
System.out.println(m);
  
// You build one that matches the account pattern.
}
}

The StringMatcher Interface We\'re going to tackle this problem by implementing several different classes that satisfy a StringMatcher interface, which specifies a single method public int match (String s, int start) match should take a string and a start index, and return -1 the given string, starting from index start, does not match the specified pattern. Otherwise it should return the index after the specified pattern ends We will implement four kinds of string patterns, each as a class that implements the String Matcher interface SOM which stands for \"single-character matcher\". This is provided for you. has a single char field, and matches the string with just that one character ROM which stands for \"range-character matcher\". You wi implement this. It has two char fields and checks that the string has a character ir between those two characters at the given start index SBA which stands for \"sequence.\" You will implement this. It has two String Matcher fields. It checks that the first StringMatcher matches at the given start index, and if it does, also checks that the second String Matcher matches after the first one STR which stands for \"string. You will implement this. It has a single String field str. It checks that the string to match against starts with str from the given start index Some examples For a string pattern like new STR(\"cs11 W\") o For matching the string \"cs11wb\" starting at index 0, it should return 5 -the index after w, where the pattern ends o For matching the string \"stuff.cs11wb\" starting at index 0, it should return -1, since stuff is not equal to CS o For matching the string \"stuff-cs11wb\" starting at index 6, it should return 11 the index after w, where the pattern ends For a single character pattern like new SDI c o For matching the string \"cs11wb\" starting at index 0, it should return 1 the index after c where the pattern ends o For matching the string \"stuff-cs11wb\" starting at index 0, it should return -1, since it doesn\'t match o For matching the string \"stuff-cs11wb\" starting at index 6, it should return 7 the index afterc, where the pattern ends For a range pattern like new R01(\'a \'z\') o For matching the string good stuff starting at index 0, it should return 1 the index after g, where the pattern ends (g matches since it is between a and z o For matching the string good stuff starting at index 5, it should return 6 the index after s, where the pattern ends (s matches because it is between a and z o For matching the string \"good Stuff\" starting at index 5, it should return -1, since Sis not between a and z For a sequence pattern like new SBA(new STR(\"cs11 w\"), new RM b c\')) o For matching the string CS wb starting at index 0, it should return 6 the index after b where the pattern ends o For matching the string CS IZ starting at index 0, it should return -1. The first part of the sequence matches, but not the second o For matching the string \"stuff cs wb morest uff\" starting at index 6, it should return 12, the index after both patterns are matched

Solution

Solution:

PFB the complete solution with full explanation as multi-line comments just above the implementation of match() for all the respective classes. [ Explanation over the implementation gives a clear idea about the context rather than explaining separately ]

interface StringMatcher {
public int match(String s, int start);
}
class SCM implements StringMatcher {
private final char c;
public SCM(char c) {
this.c = c;
}
public int match(String s, int start) {
if(s.length() <= start) { return -1; }
if(s.charAt(start) == this.c) { return start + 1; }
return -1;
}
}
class RCM implements StringMatcher {
private final char from, to;
public RCM(char from, char to) { this.from = from; this.to = to; }

/*EXPLANATION:
* Here we are checking by the help of \'>\' & \'<\' operators directly
* and if the character at the given start matches the condition
* we pass the next index value
*/
public int match(String s, int start) {
if(s.length() <= start) { return -1; }
if(s.charAt(start) >=this.from && s.charAt(start) <= this.to) { return start + 1; }
return -1;
}
}
class STR implements StringMatcher {
private final String str;
public STR(String str) { this.str = str; }

/*EXPLANATION:
* Here the string s is sliced from the \'start\' up to the length of the \'final String str\'
* used while creating the object. This will provide us our substring to match,
* and if the sliced string/sub string matches the str
* we pass the next index value i.e. index where our sub string ends i.e. start + lenght of str
*/
public int match(String s, int start) {
if(s.length() <= start) { return -1; }
if(s.substring(start, start+str.length()).equals(str)){ return start+str.length();}
return -1;
}
}
class SEQ implements StringMatcher {
private final StringMatcher first, second;
public SEQ(StringMatcher first, StringMatcher second) {
this.first = first;
this.second = second;
}

/*EXPLANATION:
* Here first the string s is passed to the match() of the first StringMatcher object i.e. \'first\',
* if it returns a valid index, then the returned index is passed to the match() for the second StringMatcher i.e.\'second\'
* as \'start\' along with the string. Reason being: if the first.match() able to match then it will return the next index
* value which is the start for the next StringMatcher
*/
public int match(String s, int start) {
if(s.length() <= start) { return -1; }
int firstMatchValue = this.first.match(s, start);
int secondMatchValue = 0;
if( firstMatchValue != -1){
secondMatchValue = this.second.match(s, firstMatchValue);
if( secondMatchValue != -1){
return secondMatchValue;
}else{
return -1;
}
}else{
return -1;
}
}
}
public class Main {
public static void main(String[] args) {
StringMatcher ti = new STR(\"testinput\");
StringMatcher oneToSix = new RCM(\'1\', \'6\');
StringMatcher dotTxt = new STR(\".txt\");

// Write some small printout tests of these individually
StringMatcher s1 = new SEQ(ti, new SEQ(oneToSix, dotTxt));
int m = s1.match(\"testinput1.txt\", 0);
System.out.println(m);

StringMatcher s2 = new SEQ(new STR(\"cs11w\"), new RCM(\'b\', \'c\'));
System.out.println(s2.match(\"cs11wb\", 0));
System.out.println(s2.match(\"cs11wZ\", 0));
System.out.println(s2.match(\"stuff_cs11wb_morestuff\", 6));
// You build one that matches the account pattern.
}
}