未使用的类无法在Eclipse中解析

Question

我正在使用Eclipse Java EE IDE进行Web开发。

版本：赫利俄斯服务版本2 版本ID：20110218-0911

目前我正在写一个书店项目中，但是编译ShoppingCart.java时，它显示

“ - 类型的java.util。 function.Consumer不能得到解决。这是间接需要的.class文件

- The type java.util.function.Consumer cannot be resolved. It is indirectly referenced from required .class 
files 

- The type java.util.function.Predicate cannot be resolved. It is indirectly referenced from required .class files 

- The type java.util.function.UnaryOperator cannot be resolved. It is indirectly referenced from 
required .class files 

- The type java.util.Comparator cannot be resolved. It is indirectly referenced from required .class files" 

开头引用。 这是Book.java

package bookstore; 

import java.io.Serializable; 

public class Book implements Serializable { 
private static final long serialVersionUID = 1L; 
private String isbn; 
private String author; 
private String title; 
private double price; 
private int edition; 
private String publisher; 
private String copyright; 
public Book(String isbn, String author, String title, double price, int edition, String publisher, String copyright) { 
    this.isbn = isbn; 
    this.author = author; 
    this.title = title; 
    this.price = price; 
    this.edition = edition; 
    this.publisher = publisher; 
    this.copyright = copyright; 
} 
public String getIsbn() { 
    return isbn; 
} 
public String getAuthor() { 
    return author; 
} 
public int getEdition() { 
    return edition; 
} 
public String getPublisher() { 
    return publisher; 
} 
public String getCopyright() { 
    return copyright; 
} 
public String getTitle() { 
    return title; 
} 
public void setTitle(String title) { 
    this.title = title; 
} 
public double getPrice() { 
    return price; 
} 
public void setPrice(double price) { 
    this.price = price; 
} 
} 

而且ShoppingCart.java

package bookstore; 
import java.util.*; 
import java.util.ArrayList; 


public class ShoppingCart extends ArrayList<Book> { 
private static final long serialVersionUID = 1L; 
public ShoppingCart() { 
} 

public void addBook(Book book) { 
    this.add(book); 
} 

public Book getBook(int i) { 
    return this.get(i); 
} 

public double getTotalPrice() { 
    double price = 0.0; 
    for (Book book : this) { 
     price += book.getPrice(); 
    } 
    return price; 
} 
} 

我不包括消费，谓语，UnaryOperator和比较器的功能。我发现，在“扩展的ArrayList”

Answer 1

这是一个恼人的Eclipse的Bug，似乎现在再咬问题可能是由于。见http://dev-answers.blogspot.de/2009/06/eclipse-build-errors-javalangobject.html

一个可能的解决方案，否则请尝试以下;

关闭该项目并重新打开它。 清洁项目（它将重建构建路径，因此与JDK库重新配置）

OR

删除并重新导入该项目，并在必要时做上述步骤一次。