此类选用的是jdk1.8.0_221版本的，在java.lang.String.java下的代码。
String类中replaceFirst方法
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 }
String类中replaceAll方法
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 }
String类中replace方法
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 }