Java三种循环求和方法

public class HundredSum { 
 public static void main(String[] args){ 
  int x=0; 
  for(int i=1;i<=100;i++){ 
   x=x+i;//x+=i; 
  } 
  System.out.print(x); 
 } 
} 

public class HundredSum { 
 public static void main(String[] args){ 
  int x=0; int i; 
  while (i<=100){ 
   x=x+i; //x+=i;
   i++; 
  } 
  System.out.print(x); 
 } 
} 

public class HundredSum{ 
 public static void main(String[] args){ 
  int i=0,x=0; 
  do{ 
   x=x+i; //x+=i;
   i++; 
  }while (i<=100); //先循环do语句块，再执行while，不满足while条件则跳出循环 
  System.out.print(x); 
 } 
}