一个java类型题目,1*1+1*2+2*3+3*4+4*5+(……)+9*10的代码怎么写的?

public class Sum {
public static void main(String []args)
{
int sum=1*1;
System.out.print("1*1");
for(int i=1;i<10;i++)
{
sum+=i*(i+1);

System.out.print("+"+i+"*"+(i+1));
}
System.out.print("="+sum);

}
}

class jisuan
{
public static void main(String[] str)
{
int a=1,sum=1;sum=1;//sum=1*1;
for(int i=1;i<10;i++)
{
a++;
sum+=i*a;
}
System.out.println();
System.out.print("sum="+sum);
}
}

public static void main(String [] args)
{
int num1 = 1;
int temp =1;
int sum=0;
for(int i =1;i<=10;i++)
{
sum+=num1*temp;
num1=i+1;
temp=i;
}
System.out.println("和为:"+sum);
}

public class Sum {
public static void main(String []args)
{
int sum=1*1