java 方法返回整数数组中奇数的个数
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method returns the number of odd numbers in the array of integers
提问by Haider
I get an error message saying:
我收到一条错误消息说：
This method must return a result of type int.
此方法必须返回 int 类型的结果。
My code:
我的代码：
public int countOdds (int[] values) {
int countOdd =0;
for (int i=0; i<values.length; i++) {
if (values[i] %2 != 0) {
countOdd++;
return countOdd;
}
}
}
回答by iluxa
Compiler thinks that the method may not return anything at all:
编译器认为该方法可能根本不返回任何内容：
public int countOdds (int[] values) {
int countOdd =0;
for (int i=0; i<values.length; i++) {
if (values[i] %2 != 0){
countOdd++;
return countOdd;
}
}
// what if this line is reached?
}
Suppose you run it with values.length = 0. What will the method return?
假设您使用values.length = 0. 该方法将返回什么？
Your returnstatement should be in a different place in code
您的return语句应该在代码中的不同位置
回答by Sam I am says Reinstate Monica
The following line
以下行
return countOdd;
should be outside of your for-loop.
应该在你的 for 循环之外。
Otherwise, you'll either return 1 when you reach the first odd, or you won't reach a return statement at all if there are no odds.
否则，您要么在达到第一个奇数时返回 1，要么在没有几率时根本不会到达 return 语句。
public int countOdds (int[] values) {
int countOdd =0;
for (int i=0; i<values.length; i++) {
if (values[i] %2 != 0) {
countOdd++;
}
}
return countOdd;
}
回答by James Waldby - jwpat7
If the valuesarray has no odd numbers in it, then your function exits without returning an int. As noted in a previous answer, move the returnstatement out of the loop.
如果values数组中没有奇数，则您的函数退出而不返回int. 如上一个答案所述，将return语句移出循环。
Also, because the value of values[i]%2is 0 for even numbers and 1 for odd numbers, the number of odd numbers is equal to the sum over iof values[i]%2, allowing you to significantly shorten the code:
此外，由于值values[i]%2是0的偶数和1奇数，奇数的个数等于求和i的values[i]%2，让您显著缩短了代码：
public int countOdds (int[] values) {
int i, count=0;
for (i=0; i<values.length; ++i) {
count += values[i]%2;
}
return count;
}
An alternative version uses bitwise AND:
另一个版本使用按位 AND：
public int countOdds (int[] values) {
int i, count=0;
for (i=0; i<values.length; ++i) {
count += values[i] & 1;
}
return count;
}
回答by qwikLup
Supposing the if-statement never returns true, will the method return anything? No, it won't, so you need to include a return statement that will execute in the event the if-statement never runs.
假设 if 语句永远不会返回 true，该方法会返回任何内容吗？不，它不会，因此您需要包含一个 return 语句，该语句将在 if 语句永远不会运行的情况下执行。
public int countOdds (int[] values) {
int countOdd =0;
for (int i=0; i<values.length; i++) {
if (values[i] %2 != 0) {
countOdd++;
}
}
return countOdd;
}
