public class Test1{
public static void main(String []args){
int l =0, u = 0, o = 0;
String s = "aB aK sL7d6hG";
StringBuffer sb1 = null;
for(int i=0; i<s.length(); i++){
char c = s.charAt(i);
if(c >= 'a' && c <= 'z'){
sb1.append(c);
l++;
}else if(c >= 'A' && c <= 'Z'){
u++;
}else {
o++;
}
System.out.print(sb1);
} System.out.println(" "+l+" "+u+" "+o);
}
}我想计算下s里面的小写字母数并输出小写字母组成的字符串
但是这样写运行的时候会报一个 java.lang.NullPointerException
这个空指针错是哪个引起的?sb1? 应该怎么办呢?
public static void main(String []args){
int l =0, u = 0, o = 0;
String s = "aB aK sL7d6hG";
StringBuffer sb1 = null;
for(int i=0; i<s.length(); i++){
char c = s.charAt(i);
if(c >= 'a' && c <= 'z'){
sb1.append(c);
l++;
}else if(c >= 'A' && c <= 'Z'){
u++;
}else {
o++;
}
System.out.print(sb1);
} System.out.println(" "+l+" "+u+" "+o);
}
}我想计算下s里面的小写字母数并输出小写字母组成的字符串
但是这样写运行的时候会报一个 java.lang.NullPointerException
这个空指针错是哪个引起的?sb1? 应该怎么办呢?
public static void main(String []args){
int l =0, u = 0, o = 0;
String s = "aB aK sL7d6hG";
StringBuffer sb1 = new StringBuffer("");
StringBuffer sb2 = new StringBuffer("");
StringBuffer sb3 = new StringBuffer("");
for(int i=0; i<s.length(); i++){
char c = s.charAt(i);
if(c >= 'a' && c <= 'z'){
sb1.append(c);
l++;
}else if(c >= 'A' && c <= 'Z'){
sb2.append(c);
u++;
}else {
sb3.append(c);
o++;
}
}
System.out.println(sb1);
System.out.println(sb2);
System.out.println(sb3);
System.out.println("小写字母数有:"+l+"个;"+"\n"+"大写字母字母数有:"
+u+"个;"+"\n"+"非字母数有:"+o+"个!");
}
}