Question

java前辈帮忙看下

public class LastIndexOf {

public int lastIndexOf(int ch,int fromIndex){
String strCom="abcdefg gfdecba";
int index = strCom.indexOf(ch, fromIndex);
return index;
}
public static void main(String[] args) {
String strCom= new String();
int i=strCom.indexOf("a", 5);
System.out.println(i);
}
}
帮忙修改下运算结果是0。新手不太懂。

Answer 1

public class LastIndexOf {

public int lastIndexOf(int ch,int fromIndex){
String strCom="abcdefg gfdecba";
int index = strCom.indexOf(ch, fromIndex);
return index;
}
public static void main(String[] args) {
LastIndexOf l = new LastIndexOf();
System.out.println(l.lastIndexOf('a',5));
}
}

Answer 2

public class LastIndexOf {

public int lastIndexOf(int ch,int fromIndex){
return 0;
}
public static void main(String[] args) {
String strCom= new String();
int i=strCom.indexOf("a", 5);
System.out.println(i);
}
}

这不就行了？

Answer 3

strCom没赋值，为空