求解答关于do...while的问题

public static void main(String[] args) {

int sum=0;

int num=2;

do {sum=sum+num;

    num=num+2;

}while(num<=50);

}

System.out.println("0到50以内的偶数的总和为："+sum);  //这一行提示有错误

}

错误信息是：

Multiple markers at this line

- Syntax error, insert ")" to complete MethodDeclaration

- Syntax error on token ".", @ expected after this token

- Syntax error, insert "SimpleName" to complete 

QualifiedName

- Syntax error, insert "Identifier (" to complete 

MethodHeaderName