如何让列表向后打印 [英] How do I get the list to print backwards
问题描述
我能够将列表从最小到最大打印，但是从最大到最小的打印时我遇到了麻烦。我不知道我做错了什么。
我尝试了什么：
import java.util.Scanner;
public class CourseGradePrinter {
public static void main（String [] args ）{
final int NUM_VALS = 4;
int [] courseGrades = new int [NUM_VALS];
int i = 0;
courseGrades [0] = 7;
courseGrades [1] = 9;
courseGrades [2] = 11 ;
courseGrades [3] = 10;
for（i = 0; i< NUM_VALS; i ++）
{
System.out.print（courseGrades [i] +）;
}
System.out.println（ ）;
for（i = NUM_VALS - 1; i> NUM_VALS; i ++）
{
System.out.print（courseGrades [i] +）;
}
返回;
}
}
I'm able to print the list from least to greatest, but I'm having trouble printing it from greatest to least. I don't know what I'm doing wrong.
What I have tried:
import java.util.Scanner;
public class CourseGradePrinter {
public static void main (String [] args) {
final int NUM_VALS = 4;
int[] courseGrades = new int[NUM_VALS];
int i = 0;
courseGrades[0] = 7;
courseGrades[1] = 9;
courseGrades[2] = 11;
courseGrades[3] = 10;
for (i = 0; i < NUM_VALS; i++)
{
System.out.print(courseGrades[i] + " ");
}
System.out.println();
for (i = NUM_VALS - 1; i > NUM_VALS; i++)
{
System.out.print(courseGrades[i] + " ");
}
return;
}
}
推荐答案
为了打印最小到最大（你没有，不是那个代码）或者最大 - 至少你需要将信息组织成一个已排序的集合。哪个阵列绝对不是。
看看排序算法（如果你的功课要求你自己实现它们，它可能会这样做）或 Java.util.Arrays.sort（int []）方法 [ ^ ]如果你被允许使用它（你可能不是）。
In order to print it least-to-greatest (which you don't, not with that code) or greatest-to-least you need to organise the info into a sorted collection. Which an array most definitely isn't.
Look at Sort algorithms (if your homework expects you to implement them yourself, and it probably does) or the Java.util.Arrays.sort(int[]) Method[^] if you are allowed to use it (you probably aren't).
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如何让列表向后打印
你已经知道 for（i = 0; i< NUM_VALS; i ++）将 i 踩0,1， 2和3.
现在你要我到第3步，第2步，第1步和第0步
起点是3所以 i = NUM_VALS - 1 没问题。
结束点为0所以你需要循环只要 i> = 0
您使用 i ++ 来增加 i 一个现在你要减少我所以我 - 就是你需要的。
有一个工具可以让你看到代码在做什么，它的名字是调试器。它也是一个很好的学习工具，因为它向你展示了现实，你可以看到哪种期望与现实相符。
当你不明白你的代码在做什么或为什么它做它做的时候，答案就是答案是调试器。
使用调试器查看代码正在执行的操作。只需设置断点并查看代码执行情况，调试器允许您逐行执行第1行并在执行时检查变量。
调试器 - 维基百科，免费的百科全书 [ ^ ]
http://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html [ ^ ]
https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html [ ^ ]
调试器在这里向您展示你的代码正在做，你的任务是与它应该做的事情进行比较。
调试器中没有魔法，它没有找到错误，它只是帮助你。当代码没有达到预期的效果时，你就会接近一个错误。
You already know that for (i = 0; i < NUM_VALS; i++) will have i stepping 0, 1, 2 and 3.
Now you want i to step 3, 2, 1 and 0
Starting point is 3 so i = NUM_VALS - 1 is ok.
Ending point is 0 so you need to loop as long as i>=0
And you used i++ to increase i and now you want to decrease i so i-- is what you need.
There is a tool that allow you to see what your code is doing, its name is debugger. It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.
Debugger - Wikipedia, the free encyclopedia[^]
http://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html[^]
https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.
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