你switch里面放个赋值语句干嘛,放数组就行了啊,而且你这逻辑也很混乱啊。你上面那里+str就行了啊。你加小写的干嘛
import java.util.Scanner;
public class ToUpCase {
public static String toUpCase(String str){
String s = "";
for(int i = 0;i < str.length();++i){
int a = (int)str.charAt(i) - 32;
char b = (char)a;
s = s + b;
}
return s;
}
public static void main(String[] args) {
System.out.println("输入字符串");
Scanner sc = new Scanner(System.in);
String str = sc.next();
System.out.println(toUpCase(str));
}
}