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59 lines (55 loc) · 1.65 KB
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package books;
/**
* @program JavaBooks
* @description: 替换空格
* @author: mf
* @create: 2019/08/18 18:27
*/
/*
请实现一个函数，把字符串中的每个空格替换成"%20"，例如
输入"We are happy."，则输出"We%20are%20happy."
*/
public class T5 {
public static void main(String[] args) {
StringBuffer s = new StringBuffer("We are happy.");
// String s1 = replaceSpace(s);
String s1 = replaceSpace2(s);
System.out.println(s1);
}
/**
* 双指针，从后往前遍历即可
* @param str
* @return
*/
public static String replaceSpace(StringBuffer str) {
int spaceNum = 0;
// 检测空格数目
for (int i = 0; i < str.length(); i++) {
if (str.charAt(i) == ' ') spaceNum++;
}
char[] s1 = new char[str.length() + 2 * spaceNum]; // 新数组的长度
int p2 = s1.length - 1; // 定义新数组的指针
for (int i = str.length() - 1; i>= 0; i--) { // 从后往前遍历
if (str.charAt(i) == ' ') {
s1[p2--] = '0';
s1[p2--] = '2';
s1[p2--] = '%';
} else {
s1[p2--] = str.charAt(i);
}
}
return new String(s1);
}
// 第二种方法，Stringbuffer的特性
public static String replaceSpace2(StringBuffer str) {
StringBuffer s1 = new StringBuffer();
for (int i = 0; i < str.length(); i++) {
if (str.charAt(i) == ' ') {
s1.append("%20");
} else {
s1.append(str.charAt(i));
}
}
return new String(s1);
}
}