Java：计算循环
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Java: Calculate for loop
提问by Michael
I've now googled around and tried various methods myself without any success. So to the problem, I've got this loop, I type in a number "n" ex. 10. Then the program counts from 1 to 10. This is the loop I'm using.
我现在已经在谷歌上搜索并尝试了各种方法，但没有任何成功。所以对于这个问题，我有这个循环，我输入一个数字“n”ex。10. 然后程序从 1 数到 10。这是我使用的循环。
n = Keyboard.readInt();
for(int e = 1; e <=n; e++)
System.out.println(e);
That works fine, but now I want to calculate the numbers that has been shown in loop so..It would be 1+2+3+4+5+6+7+8+9+10 (If 'n' was chosen as number 10) and it should give the calculation of that so it would say 1+2+3+4+5+6+7+8+9+10 = 55.
效果很好，但现在我想计算循环中显示的数字，所以..它会是 1+2+3+4+5+6+7+8+9+10（如果选择了“n”作为数字 10），它应该给出它的计算，所以它会说 1+2+3+4+5+6+7+8+9+10 = 55。
Would be great if anyone here could help me.
如果这里有人可以帮助我，那就太好了。
Thanks in advance,
提前致谢，
Michael.
迈克尔。
回答by NPE
You could do it the hard way or the easy way:
你可以用困难的方法或简单的方法来做：
The hard way:Keep a running sum and add to it inside the loop.
The easy way:Notice that the sum you're looking for equals
n*(n+1)/2(which is easy to prove).
困难的方法：保持运行总和并在循环内添加到它。
简单的方法：请注意，您正在寻找的总和等于
n*(n+1)/2（这很容易证明）。
回答by Brett Walker
StringBuilder buffer = new StringBuilder();
int n = Keyboard.readInt();
int sum = 0;
for ( int e = 1; e <=n; e++ )
{
buffer.append( "+ " + e );
sum += e;
}
System.out.println( buffer.substring( 2 ) + " = " + sum );
回答by RoflcoptrException
Do it like that:
这样做：
public static void main(String[] args) {
int n = 10;
int sum = 0;
for(int e = 1; e <=n; e++)
sum = sum + e;
System.out.println(sum);
}
回答by Daniel
int sum = 0;
for(int e = 1; e <=n; e++)
{
sum += e;
}
System.out.println(sum);
回答by Garrett Hall
Use another variable to accumulate the results.
使用另一个变量来累积结果。
回答by Bohemian
I feel like spoon-feeding, so here's the code:
我觉得像用勺子喂食，所以这是代码：
public static void main(String args[]) {
int n = Keyboard.readInt();
int total = 0;
for (int i = 1; i <= n; i++)
total += i;
System.out.println(total);
}
回答by Mike C
Try this:
试试这个：
n = Keyboard.readInt();
int total = 0;
StringBuilder arith = new StringBuilder();
for(int e = 1; e <=n; e++) {
total += e;
arith.append(e + (e < n? "+" : ""));
}
arith.append("=" + total);
System.out.println(arith.toString());
