Question

我知道我在这里做一些愚蠢的事情。我正在尝试使用java / javac从命令行编译Java。我已经浏览了许多答案，但无法理解。我可以毫无问题地编译并运行我们的好朋友HelloWorld.java。我正在尝试从 Java 8 In Action 编译代码。 .java文件是：

package lambdasinaction.chap1;
import java.util.*;
import java.util.function.Predicate;
public class FilteringApples{
    // public static void main(String ... args){
    public static void main(String[] args) {
        List<Apple> inventory = Arrays.asList(new Apple(80,"green"),
                                              new Apple(155, "green"),
                                              new Apple(120, "red"));   
        List<Apple> greenApples = filterApples(
            inventory, FilteringApples::isGreenApple);
        System.out.println(greenApples);
        List<Apple> heavyApples = filterApples(
            inventory, FilteringApples::isHeavyApple);
        System.out.println(heavyApples);
        List<Apple> greenApples2 = filterApples(inventory,
            (Apple a) -> "green".equals(a.getColor()));
        System.out.println(greenApples2);
        List<Apple> heavyApples2 = filterApples(inventory,
            (Apple a) -> a.getWeight() > 150);
        System.out.println(heavyApples2);
        List<Apple> weirdApples = filterApples(inventory,
            (Apple a) -> a.getWeight() < 80 || "brown".equals(a.getColor()));
        System.out.println(weirdApples);
    }
    public static List<Apple> filterGreenApples(List<Apple> inventory){
        List<Apple> result = new ArrayList<>();
        for (Apple apple: inventory){
            if ("green".equals(apple.getColor())) {
                result.add(apple);
            }
        }
        return result;
    }
    public static List<Apple> filterHeavyApples(List<Apple> inventory){
        List<Apple> result = new ArrayList<>();
        for (Apple apple: inventory){
            if (apple.getWeight() > 150) {
                result.add(apple);
            }
        }
        return result;
    }
    public static boolean isGreenApple(Apple apple) {
        return "green".equals(apple.getColor()); 
    }
    public static boolean isHeavyApple(Apple apple) {
        return apple.getWeight() > 150;
    }
    public static List<Apple> filterApples(
            List<Apple> inventory, Predicate<Apple> p){
        List<Apple> result = new ArrayList<>();
        for(Apple apple : inventory){
            if(p.test(apple)){
                result.add(apple);
            }
        }
        return result;
    }       
    public static class Apple {
        private int weight = 0;
        private String color = "";
        public Apple(int weight, String color){
            this.weight = weight;
            this.color = color;
        }
        public Integer getWeight() {
            return weight;
        }
        public void setWeight(Integer weight) {
            this.weight = weight;
        }
        public String getColor() {
            return color;
        }
        public void setColor(String color) {
            this.color = color;
        }
        public String toString() {
            return "Apple{" +
                   "color='" + color + '\'' +
                   ", weight=" + weight +
                   '}';
        }
    }
}

我使用“ javac -cp。FilterApples.java”对其进行了编译，并且编译时没有错误或警告。我得到两个类文件：FilteringApples $ Apple.class FilteringApples.class。我尝试了多种方式来运行它，包括“ java -cp。FilterApples”和“ java -cp。lambdasinaction.chap1.FilteringApples”。它总是与

一起返回

Error: Could not find or load main class lambdasinaction.chap1.FilteringApples

javap的输出是：

Compiled from "FilteringApples.java"
public class lambdasinaction.chap1.FilteringApples {
  public lambdasinaction.chap1.FilteringApples();
  public static void main(java.lang.String[]);
  ...

有人建议这是一个duplicate of another question。我在研究这一问题时曾看过这个问题，但建议没有奏效。而且，正如我所说，我可以毫无问题地编译HelloWorld.java。我认为这里有些不同。

我做错了什么？
谢谢

注意：“ java HelloWorld”工作正常，但是java“ FilterApples”在同一目录中失败，因为HelloWorld没有包声明，而FilterApples做到了：

package lambdasinaction.chap1;

Answer 1

在Windows上：

假设当前目录为C:\Temp\sample

第1步

创建目录lambdasinaction\chap1并将文件FilteringApples.java放在此处

第2步

在C:\Temp\sample中时，将编译代码：javac lambdasinaction\chap1\FilteringApples.java。完成此步骤后，预期输出为：

C:\temp\sample>tree /F
C:.
└───lambdasinaction
    └───chap1
            FilteringApples$Apple.class
            FilteringApples.class
            FilteringApples.java

第3步

在C:\Temp\sample中运行代码：java lambdasinaction.chap1.FilteringApples

预期输出为：

C:\temp\sample>java lambdasinaction.chap1.FilteringApples
[Apple{color='green', weight=80}, Apple{color='green', weight=155}]
[Apple{color='green', weight=155}]
[Apple{color='green', weight=80}, Apple{color='green', weight=155}]
[Apple{color='green', weight=155}]
[]

javac：找不到或加载主类

1 个答案: