收集面试题（二十三）（替换字符串）

// 实现replace函数，不要使用字符串搜索替换函数。

public class Replace {

	public static void main(String[] args) {
		String info = "system runs";

		System.out.println(replace(info, "st", "$$"));
	}

	public static String replace(String source, String toReplace, String replace) {

		if (source == null || toReplace == null || replace == null) {
			throw new RuntimeException("null is not allow.");
		}

		if (toReplace.length() > source.length()) {
			throw new RuntimeException("error replace.");
		}
		int length = toReplace.length();
		String temp = "";
		StringBuffer buffer = new StringBuffer("");
		for (int i = 0; i < source.length(); i++) {

			if (i + length > source.length()) {
				temp = source.substring(0, source.length());
			} else {
				temp = source.substring(i, i + length);
			}

			if (temp.equals(toReplace)) {
				buffer.append(replace);
				i = i + length - 1;
			} else {
				buffer.append(source.charAt(i));
			}
		}

		return buffer.toString();
	}
}