String类中replaceFirst、replaceAll、replace的代码区别（暂贴代码）

 1     /**
 2      * Replaces the first substring of this string that matches the given <a
 3      * href="../util/regex/Pattern.html#sum">regular expression</a> with the
 4      * given replacement.
 5      *
 6      * <p> An invocation of this method of the form
 7      * <i>str</i>{@code .replaceFirst(}<i>regex</i>{@code ,} <i>repl</i>{@code )}
 8      * yields exactly the same result as the expression
 9      *
10      * <blockquote>
11      * <code>
12      * {@link java.util.regex.Pattern}.{@link
13      * java.util.regex.Pattern#compile compile}(<i>regex</i>).{@link
14      * java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(<i>str</i>).{@link
15      * java.util.regex.Matcher#replaceFirst replaceFirst}(<i>repl</i>)
16      * </code>
17      * </blockquote>
18      *
19      *<p>
20      * Note that backslashes ({@code \}) and dollar signs ({@code $}) in the
21      * replacement string may cause the results to be different than if it were
22      * being treated as a literal replacement string; see
23      * {@link java.util.regex.Matcher#replaceFirst}.
24      * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
25      * meaning of these characters, if desired.
26      *
27      * @param   regex
28      *          the regular expression to which this string is to be matched
29      * @param   replacement
30      *          the string to be substituted for the first match
31      *
32      * @return  The resulting {@code String}
33      *
34      * @throws  PatternSyntaxException
35      *          if the regular expression‘s syntax is invalid
36      *
37      * @see java.util.regex.Pattern
38      *
39      * @since 1.4
40      * @spec JSR-51
41      */
42     public String replaceFirst(String regex, String replacement) {
43         return Pattern.compile(regex).matcher(this).replaceFirst(replacement);
44     }

 1 /**
 2      * Replaces each substring of this string that matches the given <a
 3      * href="../util/regex/Pattern.html#sum">regular expression</a> with the
 4      * given replacement.
 5      *
 6      * <p> An invocation of this method of the form
 7      * <i>str</i>{@code .replaceAll(}<i>regex</i>{@code ,} <i>repl</i>{@code )}
 8      * yields exactly the same result as the expression
 9      *
10      * <blockquote>
11      * <code>
12      * {@link java.util.regex.Pattern}.{@link
13      * java.util.regex.Pattern#compile compile}(<i>regex</i>).{@link
14      * java.util.regex.Pattern#matcher(java.lang.CharSequence) matcher}(<i>str</i>).{@link
15      * java.util.regex.Matcher#replaceAll replaceAll}(<i>repl</i>)
16      * </code>
17      * </blockquote>
18      *
19      *<p>
20      * Note that backslashes ({@code \}) and dollar signs ({@code $}) in the
21      * replacement string may cause the results to be different than if it were
22      * being treated as a literal replacement string; see
23      * {@link java.util.regex.Matcher#replaceAll Matcher.replaceAll}.
24      * Use {@link java.util.regex.Matcher#quoteReplacement} to suppress the special
25      * meaning of these characters, if desired.
26      *
27      * @param   regex
28      *          the regular expression to which this string is to be matched
29      * @param   replacement
30      *          the string to be substituted for each match
31      *
32      * @return  The resulting {@code String}
33      *
34      * @throws  PatternSyntaxException
35      *          if the regular expression‘s syntax is invalid
36      *
37      * @see java.util.regex.Pattern
38      *
39      * @since 1.4
40      * @spec JSR-51
41      */
42     public String replaceAll(String regex, String replacement) {
43         return Pattern.compile(regex).matcher(this).replaceAll(replacement);
44     }

 1 /**
 2      * Replaces each substring of this string that matches the literal target
 3      * sequence with the specified literal replacement sequence. The
 4      * replacement proceeds from the beginning of the string to the end, for
 5      * example, replacing "aa" with "b" in the string "aaa" will result in
 6      * "ba" rather than "ab".
 7      *
 8      * @param  target The sequence of char values to be replaced
 9      * @param  replacement The replacement sequence of char values
10      * @return  The resulting string
11      * @since 1.5
12      */
13     public String replace(CharSequence target, CharSequence replacement) {
14         return Pattern.compile(target.toString(), Pattern.LITERAL).matcher(
15                 this).replaceAll(Matcher.quoteReplacement(replacement.toString()));
16     }