模仿String.indexOf,判斷一個字符串是否包含另一個字符串

 

目錄：
一.方法介紹
二.圖示意
三.源代碼

一.方法介紹

判斷一個字符串str1是否包含另一個字符串str2：
1.取str2的第一個字符一次和str1的字符依次比較，知道找到相等的字符爲止或者找完整個str1的length.
2.當找到相等的字符後，在str2長度內str2與str1依次進行比較

二.圖示意



三.源代碼

JDK中java.lang.String.indexOf(char[], int, int, char[], int, int, int)源碼:

/**
     * Code shared by String and StringBuffer to do searches. The
     * source is the character array being searched, and the target
     * is the string being searched for.
     *
     * @param   source       the characters being searched.
     * @param   sourceOffset offset of the source string.
     * @param   sourceCount  count of the source string.
     * @param   target       the characters being searched for.
     * @param   targetOffset offset of the target string.
     * @param   targetCount  count of the target string.
     * @param   fromIndex    the index to begin searching from.
     */
    static int indexOf(char[] source, int sourceOffset, int sourceCount,
                       char[] target, int targetOffset, int targetCount,
                       int fromIndex) {
    if (fromIndex >= sourceCount) {
            return (targetCount == 0 ? sourceCount : -1);
    }
        if (fromIndex < 0) {
            fromIndex = 0;
        }
    if (targetCount == 0) {
        return fromIndex;
    }

        char first  = target[targetOffset];
        int max = sourceOffset + (sourceCount - targetCount);

        for (int i = sourceOffset + fromIndex; i <= max; i++) {
            /* Look for first character. */
            if (source[i] != first) {
                while (++i <= max && source[i] != first);
            }

            /* Found first character, now look at the rest of v2 */
            if (i <= max) {
                int j = i + 1;
                int end = j + targetCount - 1;
                for (int k = targetOffset + 1; j < end && source[j] ==
                         target[k]; j++, k++);

                if (j == end) {
                    /* Found whole string. */
                    return i - sourceOffset;
                }
            }
        }
        return -1;
    }

/**
     * Code shared by String and StringBuffer to do searches. The
     * source is the character array being searched, and the target
     * is the string being searched for.
     *
     * @param   source       the characters being searched.
     * @param   sourceOffset offset of the source string.
     * @param   sourceCount  count of the source string.
     * @param   target       the characters being searched for.
     * @param   targetOffset offset of the target string.
     * @param   targetCount  count of the target string.
     * @param   fromIndex    the index to begin searching from.
     */
    static int indexOf(char[] source, int sourceOffset, int sourceCount,
                       char[] target, int targetOffset, int targetCount,
                       int fromIndex) {
	if (fromIndex >= sourceCount) {
            return (targetCount == 0 ? sourceCount : -1);
	}
    	if (fromIndex < 0) {
    	    fromIndex = 0;
    	}
	if (targetCount == 0) {
	    return fromIndex;
	}

        char first  = target[targetOffset];
        int max = sourceOffset + (sourceCount - targetCount);

        for (int i = sourceOffset + fromIndex; i <= max; i++) {
            /* Look for first character. */
            if (source[i] != first) {
                while (++i <= max && source[i] != first);
            }

            /* Found first character, now look at the rest of v2 */
            if (i <= max) {
                int j = i + 1;
                int end = j + targetCount - 1;
                for (int k = targetOffset + 1; j < end && source[j] ==
                         target[k]; j++, k++);

                if (j == end) {
                    /* Found whole string. */
                    return i - sourceOffset;
                }
            }
        }
        return -1;
    }

模仿的判斷一個字符串是否包含另一個字符串的源碼：

public static String compareDoubleString(String source, String target) {
        // 分別獲取兩個字符串的長度，因爲後面會用到
        int sourceLength = source.length();
        int targetLength = target.length();

        // 獲取目標的第一個字符
        char firstTargetChar = target.charAt(0);

        // 最多比較的次數
        int max = sourceLength - targetLength;
        // 如果第一個不相等，那麼一直找到相等的那一個或者找完都不能找到
        int sourceOffset = -1;
        while (++sourceOffset < max
                && source.charAt(sourceOffset) != firstTargetChar) {
        }
        if (sourceOffset <= max) {
            // 設置新的源索引
            int newSourceOffset = sourceOffset + 1;
            // 剩餘的比較長度，也就是在offset上增加targetLength
            int leaveLength = newSourceOffset + targetLength - 1;
            int targetOffset = 1;
            // 連續的比較，條件不符合的時候跳出
            for (; newSourceOffset < leaveLength
                    && source.charAt(newSourceOffset) == target
                            .charAt(targetOffset); newSourceOffset++, targetOffset++)
                ;
            if (newSourceOffset == leaveLength) {
                return "包含：source包含target字符串!";
            }
        }
        return "不包含：source不包含target字符串!";
    }

public static String compareDoubleString(String source, String target) {
		// 分別獲取兩個字符串的長度，因爲後面會用到
		int sourceLength = source.length();
		int targetLength = target.length();

		// 獲取目標的第一個字符
		char firstTargetChar = target.charAt(0);

		// 最多比較的次數
		int max = sourceLength - targetLength;
		// 如果第一個不相等，那麼一直找到相等的那一個或者找完都不能找到
		int sourceOffset = -1;
		while (++sourceOffset < max
				&& source.charAt(sourceOffset) != firstTargetChar) {
		}
		if (sourceOffset <= max) {
			// 設置新的源索引
			int newSourceOffset = sourceOffset + 1;
			// 剩餘的比較長度，也就是在offset上增加targetLength
			int leaveLength = newSourceOffset + targetLength - 1;
			int targetOffset = 1;
			// 連續的比較，條件不符合的時候跳出
			for (; newSourceOffset < leaveLength
					&& source.charAt(newSourceOffset) == target
							.charAt(targetOffset); newSourceOffset++, targetOffset++)
				;
			if (newSourceOffset == leaveLength) {
				return "包含：source包含target字符串!";
			}
		}
		return "不包含：source不包含target字符串!";
	}