给定字符串String str=“aaaaabbbbbccccddddaa”，输出 a7b5c4d4;

public class StringDemo {
public static void main(String[] args){

String str = "aaaabbbbccccdddda";

//分别为四个字母定义计数器；

int count1 = 0;
int count2 = 0;
int count3 = 0;
int count4 = 0;

char[] c = str.toCharArray();   //将字符串转换成字符数组；
for(int i =0;i<c.length;i++){
if(c[i]=='a'){
count1++;
}else if(c[i]=='b'){
count2++;
}else if(c[i]=='c'){
count3++;
}else if(c[i]=='d'){
count4++;
}
}
System.out.println("a"+count1+"b"+count2+"c"+count3+"d"+count4);
}
}