Question

对于我来说，如何在方法内部使用布尔值以及如何将其设置为false尚不十分清楚。通常，如果在方法内部使用变量，则将其分配给局部变量，是否对布尔值执行相同的操作，或者只是使用并更改它们。
我们为什么要为属性分配局部变量？如果不这样做会发生什么？
如何将设置器用作布尔值？
在有人借书后如何减小arraylist的大小？

    public class Governance{
                    ArrayList<Intenger> Books=new ArrayList<Integer>(10);
                    private boolean active = true;


            public void borrowBook{
 /** does I assign active to a local variable? why do we assign attributes  
 to a local variable? what happens if we  dont?why I cant just use and 
 initialize (e.g. set a value) the  attribute as a I defined(best practices)**//
    boolean checkStatus = isActive(); //correct?

            if(Books.isEmpty()){
            //how to I set active to false (best practices)
            checkStatus = myFunction(); //correct or are there better ways to do it?
            }
                else if(!Books.isEmpty() && isActive){
                    System.out.println("You can borrow that book");

                else{
                System.out.println("You can not borrow that book");
                }


         }

            public static boolean myFunction(){
                return false;
            }

            public boolean isActive() {
                return active;
            }

            //what is a case where I use this and how?
            public void setActive(boolean active) {
            this.active = active;
            }

        }

Answer 1

boolean是原始数据类型。您可以像其他基元一样分配它： boolean active = true; active = false;
也可以比较active == true
用作条件if(active) { // do stuff }不需要active == true

active

Governance具有覆盖整个类的范围。
如果其他某个类想要更改其值，则需要调用yourGovernanceInstance.setActive(false);因此我们将此类实例的active属性更改为false。
请参见上面的示例。

我很难使用格式化程序共享代码，请参见this link以获取简洁的版本。仅在目标链接过期时才在下方。

import java.util.ArrayList;
import java.util.List;
import java.lang.Integer;

public class Governance {
  // usually we write variables in lower case.
  private List<Integer> books = new ArrayList<Integer>();
  // private member. To change it's value it's best practice to call setters and getters to change the value.
  private boolean active = true;

  public void borrowBook() {
    if(books.isEmpty()){
    // I use "this" to refer to this class's method "isActive()"
    } else if(!books.isEmpty() && this.isActive()){
      System.out.println("You can borrow that book");
    } else {
      System.out.println("You can not borrow that book");
    }
  }

  public boolean isActive() {
    return active;
  }

  // You habe a class that has many Governance instances, e.g.
  // Governance myGov = new Governance();
  // myGov is no more active, so you call: myGov.setActive(false);
  public void setActive(boolean active) {
    this.active = active;
  }
}

您也可以只使用else if(!books.isEmpty() && active)。

取决于。通常，ArrayList在您的上下文中将包含Book个对象。您必须确定某人想拿的书。

公共课本{ 私人int ID；私有字符串标题；私有布尔活动状态； </ p>
```
public Book(int id, String title, boolean active) {
    this.id = id;
    this.title = title;
    this.active = active;
}

// Setters and Getters
```
}

在您的Governance类中：

  public boolean canBorrowBookWithId(int id) {
      Book bookToBeBorrowed = books.get(id);
      boolean canBorrow = true;
      // If book can is active, it can't be borrowed.
      if(bookToBeBorrowed.IsActive()){
        canBorrow = false;
      } else {
        // If not; set it to be and lend it out :-)  
        bookToBeBorrowed.setActive(true);
      }
      return canBorrow;
  }

旁注：canBorrowBookWithId（）检查该书是否可用以及设置它的状态。通过干净的代码，一种方法只能做一个一次完成这些操作！

您正在尝试学习Object oriented programming，这很难开始，但是最终您会继续：:）

布尔分配方法内部是否为局部变量？

1 个答案: