Convert literals to constants, add javadoc to resolver class

src/java/JavaFileStorage/app/src/main/java/keepass2android/javafilestorage/SshConfigCsvValueResolver.java

@@ -6,33 +6,70 @@ import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 
+/**
+ * A class that manipulates CSV String values based on a list of CSV "spec" definitions, where each definition
+ * can describe one of the following:
+ *
+ *   - Prepend to existing list: +something
+ *   - Append to end of existing list: something+
+ *   - Remove a specific value: -something
+ *   - Remove values matching prefix: -something*
+ *   - Remove values matching suffix: -*something
+ *   - Remove values matching substring: -*something*
+ *   - Remove values matching prefix and suffix: -some*thing
+ *
+ *  Otherwise CSV of values completely replace original config values
+ *  
+ *  Examples:
+ *  <code>
+ *    var r = new SshConfigCsvValueResolver("foo", "addToEnd+,-remove*,+addToBeginning,-*del*");
+ *    r.resolve("one,removeTwo,three,removeThree,four") --> "addToBeginning,one,three,four,addToEnd"
+ *    r.resolve("one,my-del,del-me,two,foodelbar,three") --> "addToBeginning,one,two,three,addToEnd"
+ *
+ *    r = new SshConfigCsvValueResolver("foo", "replace,the,config");
+ *    r.resolve("one,two,three,four") --> "replace,the,config"
+ *  </code>
+ *
+ */
 class SshConfigCsvValueResolver {
     interface Matcher {
         boolean matches(String s);
     }
     private final String cfgKey;
     private static final String TAG = "KP2AJFS[sshcfg]";
+
+    private static final String DELIM = ",";
+    private static final char ADD = '+';
+    private static final char REMOVE = '-';
+    private static final char WILD = '*';
     private final List<String> prepends;
     private final List<String> appends;
     private final List<Matcher> removes;
     private final List<String> replaces;
 
+    /**
+     * Creates a new resolver.
+     *
+     * @param cfgKey - configuration key name (used for logging)
+     * @param incomingSpec - A CSV String of "spec" definitions that will be used to
+     *                     (potentially) modify incoming CSV String values.
+     */
     SshConfigCsvValueResolver(String cfgKey, String incomingSpec) {
         List<String> prepends = new ArrayList<>();
         List<String> appends = new ArrayList<>();
         List<Matcher> removes = new ArrayList<>();
         List<String> replaces = new ArrayList<>();
 
-        for (String iVal : incomingSpec.split(",")) {
+        for (String iVal : incomingSpec.split(DELIM)) {
             if (iVal.isBlank()) {
                 continue;
             }
             int evLen = iVal.length();
-            if (iVal.startsWith("+") && evLen > 1) {
+            if (iVal.charAt(0) == ADD && evLen > 1) {
                 prepends.add(iVal.substring(1));
-            } else if (iVal.endsWith("+") && evLen > 1) {
+            } else if (iVal.charAt(iVal.length() - 1) == ADD && evLen > 1) {
                 appends.add(iVal.substring(0, evLen - 1));
-            } else if (iVal.startsWith("-") && evLen > 1) {
+            } else if (iVal.charAt(iVal.length() - 1) == REMOVE && evLen > 1) {
                 removes.add(createMatcher(iVal.substring(1)));
             } else {
                 // This looks like a straight replace
@@ -46,6 +83,13 @@ class SshConfigCsvValueResolver {
         this.replaces = Collections.unmodifiableList(replaces);
     }
 
+    /**
+     * Takes a CSV String and (potentially) modifies it according to the "spec" entries of this resolver.
+     *
+     * @param existingValues - the original CSV String
+     * @return an updated representation of <code>existingValues</code>, based on the defined "spec"
+     *         entries of this resolver.
+     */
     public String resolve(String existingValues) {
         List<String> newValues;
         // If there's even one replace, it wins over everything and the rest is thrown out
@@ -60,12 +104,12 @@ class SshConfigCsvValueResolver {
             // Otherwise we rebuild from existing and incoming values
             newValues = createResolvedValues(existingValues);
         }
-        return String.join(",", newValues);
+        return String.join(DELIM, newValues);
     }
 
     private List<String> createResolvedValues(String existingValues) {
         List<String> newValues = new ArrayList<>(prepends);
-        for (String a : existingValues.split(",")) {
+        for (String a : existingValues.split(DELIM)) {
             if (!shouldRemove(a)) {
                 newValues.add(a);
             }
@@ -88,7 +132,7 @@ class SshConfigCsvValueResolver {
         final String v = normalize(val);
         Matcher impl = s -> v.equals(s);
 
-        int wildcardIdx = v.indexOf('*');
+        int wildcardIdx = v.indexOf(WILD);
         if (wildcardIdx < 0) {
             return impl;
         }
@@ -100,15 +144,15 @@ class SshConfigCsvValueResolver {
         String prefix = null;
         int vLen = v.length();
 
-        if (v.charAt(0) == '*' && vLen > 1) {
-            if (vLen > 2 && v.charAt(vLen - 1) == '*') {
+        if (v.charAt(0) == WILD && vLen > 1) {
+            if (vLen > 2 && v.charAt(vLen - 1) == WILD) {
                 //substring
                 subStr = v.substring(1, vLen - 1);
             } else {
                 // endsWith
                 suffix = v.substring(1);
             }
-        } else if (v.charAt(vLen - 1) == '*' && vLen > 1) {
+        } else if (v.charAt(vLen - 1) == WILD && vLen > 1) {
             // beginsWith
             prefix = v.substring(0, v.length() - 1);
         } else if (wildcardIdx > 0) {