思路:从后往前复制,数组长度会增加,或使用StringBuilder、StringBuffer类
代码:
public class Offer_04 {
public String replaceSpace(String str){
if(str == null||str.length()<=0)//str == null判断字符串是个null指针,str.length()<=0判断字符串是空字符串
return null;
StringBuilder sb = new StringBuilder();
for(int i = 0;i<str.length();i++){
if(String.valueOf(str.charAt(i)).equals(" ")){//String.valueOf():Returns the string representation of the char argument.
sb.append("%20");
}else{
sb.append(str.charAt(i));
}
}
return String.valueOf(sb);
}
public static void main(String[] args) {
Offer_04 of4 = new Offer_04();
//测试用例
//1,输入的字符串中包含空格(空格位于字符串的最前面,空格位于字符串的最后面,空格位于字符串的中间,字符串中有连续多个空格)。
String str1 = " We are happy.";
System.out.println(of4.replaceSpace(str1));
String str2 = "We are happy. ";
System.out.println(of4.replaceSpace(str2));
String str3 = "We are happy.";
System.out.println(of4.replaceSpace(str3));
//2,输入的字符串中没有空格
String str4 = "Wearehappy.";
System.out.println(of4.replaceSpace(str4));
//特殊输入测试(字符串是个null指针 、字符串是个空字符串、字符串只有一个空格字符、字符串只有连续多个空格)。
String str5 = null;
System.out.println(of4.replaceSpace(str5));
String str6 = "";//""表示空字符串
System.out.println(of4.replaceSpace(str6));
String str7 = " ";//" "表示一个空格字符
System.out.println(of4.replaceSpace(str7));
String str8 = " ";//" "表示3个空格字符
System.out.println(of4.replaceSpace(str8));
}
}
/**
* StringBuilder a = new StringBuilder("we are happy.");
* String b = " " + a;//将StringBuilder类型转换成String类型
* StringBuilder a = new StringBuilder(a);//将String类型转换为StringBuilder类型
* */
输出结果: