如何从java中的向量向量打印
我刚开始Java编程。我正在做编程挑战书中的一些问题。问题是打印出给定整数集的最大循环长度。这是我的密码:
public class JavaApplication9 {
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
// TODO code application logic here
System.out.println("This is a program that calculates the maximum"
+ " cyclelength of two integers between 1 and 1000000");
Scanner keyboard = new Scanner(System.in);
System.out.print("Enter the first number: ");
int x = keyboard.nextInt();
System.out.println();
System.out.print("Enter the second number: ");
int y = keyboard.nextInt();
@SuppressWarnings("UseOfObsoleteCollectionType")
Vector<Integer> cycleVec = new Vector<Integer>();
Vector newVec = new Vector();
if (x <= 0 || y <= 0 || x >= 1000000 || y >= 1000000)
System.out.println("Wrong input. Input must be greater than 0"
+ " and less than 1,000,000!!");
else{
for(int k = Math.min(x, y);k<=Math.max(x, y);k++){
// We have to count 1 also
cycleVec.add(1 + cycleLength(k));
newVec.add(numList(k));
}
Enumeration vEnum = cycleVec.elements();
while(vEnum.hasMoreElements()){
int a = (int) vEnum.nextElement();
display(newVec, x, y, a);
}
System.out.println("\nElements in vector of cyclelengths:");
while(vEnum.hasMoreElements())
System.out.print(vEnum.nextElement() + " ");
System.out.println();
Object obj = Collections.max(cycleVec);
System.out.printf("%d %d ", x, y);
System.out.println(obj);
}
}
public static int cycleLength(int x){
int termPoint = 0;
int count = 0;
while (termPoint != 1){
if (x % 2 == 0){
x = x/2;
termPoint = x;
}else{
x = x*3 + 1;
termPoint = x;
}
++count;
}
return count;
}
public static Vector numList(int x){
int termPoint = 0;
Vector vec = new Vector();
while (termPoint != 1){
if (x % 2 == 0){
x = x/2;
termPoint = x;
}else{
x = x*3 + 1;
termPoint = x;
}
vec.addElement(x);
}
return vec;
}
public static void display(Vector v, int x, int y, int size){
System.out.println("Elements generated:");
int m = 0;
for(int k = Math.min(x, y); k <= Math.max(x, y); k++){
System.out.print("Number " + k + " ");
for (int i = 0; i < v.size(); i++){
for (int j = 0; j < size; j++){
m = (int)((Vector)v.elementAt(i)).elementAt(j);
System.out.print(m + " ");
}
System.out.println();
}
}
}
}
输出是
run:
This is a program that calculates the maximum cyclelength of two integers between 1 and 1000000
Enter the first number: 201
Enter the second number: 210
Elements generated:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 18 >= 18
at java.util.Vector.elementAt(Vector.java:474)
Number 201604 302 151 454 227 682 341 1024 512 256 128 64 32 16 8 4 2 1 at javaapplication9.JavaApplication9.display(JavaApplication9.java:95)
at javaapplication9.JavaApplication9.main(JavaApplication9.java:44)
Java Result: 1
BUILD SUCCESSFUL (total time: 5 seconds)
代码的第一部分起作用(如果删除显示功能)。我只想打印出每个整数x,生成的整数列表,循环长度列表和最大循环长度。还有什么方法可以使这段代码更高效(减少代码行数)
显示屏的新代码(正常工作)
public static void display(Vector v){
System.out.println("Elements generated:");
int m = 0, w = 0;
for (int i = 0; i < v.size(); i++){
Vector inner = (Vector)v.elementAt(i);
System.out.println("Number ");
for (int j = 0; j < inner.size(); j++){
m = (int)inner.elementAt(j);
if (j == 0){
if (m % 2 == 0){
w = (m-1)/3;
}else{
w = m * 2;
}
System.out.print(w + " ");
}
System.out.print(m + " ");
}
System.out.println();
}
}
# 1 楼答案
display
方法的最后一个参数是一个用作内部向量大小的整数,但是在顶部我们看到它实际上比大小大一个,因为这行:您需要考虑
cycleVec
值用于display
方法中的向量循环的正确限制异常意味着您试图访问向量中比它更多的条目。你在同一条线上有两个呼叫
elementAt
。看来这是第二个失败的参考。这意味着j
太大,这意味着size
参数不正确。访问内部阵列的安全方法如下: