将一个字符串进行反转；获取一个字符串在另一个字符串中出现的次数；获取两个字符串中最大相同子串。

1.将一个字符串进行反转。将字符串中指定部分进行反转。比如将“abcdefg”反转为”abfedcg”

 2.获取一个字符串在另一个字符串中出现的次数。 比如：获取“ab”在 “abkkcadkabkebfkabkskab”中出现的次数

package string;

/*
 * 1.将一个字符串进行反转。将字符串中指定部分进行反转。比如将“abcdefg”反转为”abfedcg”
 */
public class Test1 {
    public static void main(String[] args) {
        String str2 = "abcdefg";
        String str3 = reverseString(str2, 2, 5);
        System.out.println(str3);
    }

    public static String reverseString(String str, int start, int end) {
        String str1 = str.substring(0, start);
        for (int i = end; i >= start; i--) {
            char c = str.charAt(i);
            str1 += c;
        }
        str1 += str.substring(end + 1);
        return str1;
    }
}

package string;

public class Test2 {
    /*
     * 2.获取一个字符串在另一个字符串中出现的次数。 比如：获取“ab”在 “abkkcadkabkebfkabkskab”中出现的次数
     */
    public static void main(String[] args) {
        int i = getTime("abkkcadkabkebfkabkskab", "abk");
        System.out.println(i);
    }

    public static int getTime(String str1, String str2) {
        int count = 0;
        int len;
        while ((len = str1.indexOf(str2)) != -1) {
            count++;
            str1 = str1.substring(len + str2.length());
        }
        return count;
    }
}

package string;

/*
 * 3.获取两个字符串中最大相同子串。比如：str1 = "abcwerthelloyuiodef";str2 = "cvhellobnm"
 */
public class Test3 {
    public static void main(String[] args) {
        String str1 = "abcwerthelloyuiodef";
        String str2 = "cvhellobnm";
        StringBuilder str = getMaxSubString(str1, str2);
        System.out.println(str);
    }

    public static StringBuilder getMaxSubString(String str1, String str2) {
        String maxStr = (str1.length() > str2.length()) ? str1 : str2;
        String minStr = (str1.length() < str2.length()) ? str1 : str2;
        int len = minStr.length();
        StringBuilder sb=new StringBuilder();
        for (int i = 0; i < len; i++) {
            for (int x = 0, y = len - i; y <= len; x++, y++) {
                String str = minStr.substring(x, y);
                if (maxStr.contains(str)) {
                    sb.append(str);
                }
            }
            if(sb.length()!=0){
                return sb;
            }
        }
        return null;
    }

}