二元运算符'<=','+='的错误操作数类型
我不明白为什么我的二进制操作数不适用于 if 语句。例如，我收到错误，二元运算符“<=”的错误操作数类型。第一种：double[] 第二种：double for if(prices <=5.00)
public class Prices2
{
public static void main (String[] args)
{
double[] prices = {2.45, 7.85, 1.35, 1.55, 4.05, 9.55, 4.55, 1.45, 7.85, 1.25, 5.55, 10.95, 8.55,
2.85, 11.05, 1.95, 5.05, 8.15, 10.55, 1.05};
double average;
double total = 0.0;
int i;
for (i = 0; i < 20; i++)
{
total += prices;
}
System.out.println("Sum of all prices: "+total+"n" );
for (i = 0; i < 20; i++)
{
if (prices <= 5.00){
System.out.println(prices + " is less than $5.00");
}
}
average = total / (20);
System.out.println("nThe average price is " + average + "n");
for (i = 0; i < 20; i++)
{
if (prices >= average) {
System.out.println( " Values above average: " + prices);
}
}
}
}
回答
由于价格是一个数组 (double[]) 并且 5.00 是一个单双，因此检查“价格 <= 5.00”是没有意义的。这就像说“如果 [1.2, 3.4, 5.7, 6.2, 3.4] < 5.00”。所以编译器会用这种措辞抱怨。
更新 3/18 每个后续问题：
简短的回答是用价格 [i] 变量替换价格变量以匹配检查每个点的迭代，因为这似乎是计算的目标。此外，您不需要在顶层声明“i”。您可以在每个 for 循环中执行此操作，这样一个循环就不会意外地影响另一个循环。
public class Prices {
public static void main(String[] args) {
// Set up a list of TEST prices to check for various conditions
double[] prices = { 2.45, 7.85, 1.35, 1.55, 4.05, 9.55, 4.55, 1.45, 7.85, 1.25, 5.55, 10.95, 8.55,
2.85, 11.05, 1.95, 5.05, 8.15, 10.55, 1.05 };
int numberOfPrices = prices.length;
// GOAL: Calculate Sum of all numbers
// For each price (i=0, 1, 2... 19), add THAT price to the current value of total
double total = 0.0;
for (int i = 0; i < numberOfPrices; i++) {
total += prices[i];
}
System.out.println("Sum of all prices: " + total + "n");
// GOAL: Check for for those less than 5
// For each price (i=0, 1, 2... 19), see if THAT price is less than 5.00
for (int i = 0; i < numberOfPrices; i++) {
if (prices[i] <= 5.00) {
System.out.println(prices[i] + " is less than $5.00");
}
}
// Calculate the average price (without hard-coding)
double average;
// average = total / (20);
average = total / numberOfPrices;
System.out.println("nThe average price is " + average + "n");
// GOAL: Check for Above Average numbers
// For each price (i=0, 1, 2... 19), see if THAT price is above the average we computed before
for (int i = 0; i < numberOfPrices; i++) {
if (prices[i] >= average) {
System.out.println(" Values above average: " + prices[i]);
}
}
}
}