面试时经常考的------对字符串的操作（三）

/**
 * 假如有字符串“6sabcsssfsfs33” ，用最有快速的方法去掉字符“ab3 “
 * 
 */

// =======第一种方法======
    public static void replaceString(String str) {
        char myChar[] = str.toCharArray();
        int len = myChar.length;
        String tempStr = "";
        for (int i = 0; i < len; i++) {
            if ('a' == myChar[i] || 'b' == myChar[i] || '3' == myChar[i]) {
                myChar[i] = ' ';
            }
            String temp = "";
            temp = myChar[i] + "";
            tempStr += temp.trim();
        }
        System.out.println(tempStr);
    }

    // =======第二种方法======
    public static void replaceString2(String str) {
        char s[] = str.toCharArray();
        int len = str.length();
        char string[] = new char[14];
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < len; i++) {
            if ('a' != s[i] && 'b' != s[i] && '3' != s[i]) {
                // string[i] = s[i];
                sb.append(s[i]);
            }
            // String temp = null;
            // temp = string[i] + "";
            // sb.append(temp.trim());

        }
        System.out.println(sb.toString());
    }

    // =======第三种方法======
    public static String replaceString3(String des, String reg) {
        StringBuilder buf = new StringBuilder(des.length());
        char[] chars = des.toCharArray();
        char[] regchars = reg.toCharArray();
        for (char c : chars) {
            boolean b = true;
            for (char regchar : regchars) {
                if (c == regchar) {
                    b = false;
                    break;
                }
            }
            if (b)
                buf.append(c);
        }
        return buf.toString();
    }

    // =======第四种方法======
    public static void replaceString4(String str) {
        // 指定为字符串的正则表达式必须首先被编译为此类的实例
        Pattern pattern = Pattern.compile("[^a|b|3]"); // ^非 ; 边界匹配器"^"行的开头
        // 然后，可将得到的模式用于创建 Matcher
        // 对象，依照正则表达式，该对象可以与任意字符序列匹配。执行匹配所涉及的所有状态都驻留在匹配器中，所以多个匹配器可以共享同一模式。
        Matcher matcher = pattern.matcher(str);
        String temp = "";
        while (matcher.find()) {
            temp += matcher.group();// 返回由以前匹配操作所匹配的输入子序列
        }
        System.out.println(temp);
    }

    // =======第五种方法======
    public static void replaceString5(String str) {
        StringBuffer sb = new StringBuffer();
        Scanner scanner = new Scanner(str);
        // 匹配扫描
        scanner.findInLine("(//S*)ab(//S*)33(//S*)");
        // 返回此扫描器所执行的最后扫描操作的匹配结果
        MatchResult ms = scanner.match();
        for (int i = 1; i < ms.groupCount(); i++) { // 注意i的初始值
            sb.append(ms.group(i));
        }
        scanner.close();
        System.out.println(sb);
    }

    // =======第六种方法======
    public static String replaceString6(String str, String toRemove) {
        boolean[] removeMap = new boolean[255];
        char[] originChars = str.toCharArray();
        char[] todoChars = toRemove.toCharArray();
        char[] destChars = null;
        int strLen = 0;

        // build toRemove chars map
        for (int i = 0; i < todoChars.length; i++) {
            removeMap[(todoChars[i] & 0xFF)] = true;
        }

        for (int i = 0; i < originChars.length; i++) {
            if (removeMap[(originChars[i] & 0xff)]) {
                if (destChars == null) {
                    destChars = new char[originChars.length - 1];
                    System.arraycopy(originChars, 0, destChars, 0, i);
                }

            } else {
                if (destChars != null) {
                    destChars[strLen] = originChars[i];
                }
                strLen++;
            }
        }
        return destChars == null ? str : new String(destChars, 0, strLen);
    }