java中的容器Collection

雨点打透心脏的1/2处 2022-04-06 09:40 225阅读 0赞

# java中的容器 #

1136

1个图，

1个类(Collections)，

三个知识点(增强的for循环，Generic（泛型）,Auto-boxing/boxing(自动打包/解包))，

6个接口：

## Interface Collection<E> ##

## Interface Set<E> ##

## Interface List<E> ##

## Interface Map<K,V> ##

## Interface Iterator<E> ##

## Interface Comparable<T> ##

一个图：

![f1f3c62a-cdc7-3aba-86ab-11a561f4d305.png][]

TestCollect.java

import java.util.*;
    //java中的容器
    //一个图，8个接口
    public class TestCollection {
    	public static void main(String[] args) {
    		
    		//父类的引用指向子类的对象，多态
    		Collection c = new ArrayList();		
    		//add()添加对象
    		c.add("hello");
    		c.add(new Name("f1","l1"));
    		c.add(new Integer(100));
    		
    		System.out.println(c.size());//3
    		System.out.println(c);//[hello, f1 l1, 100]
    				
    	}
    }
    
    class Name{
    	private String firstName,lastName;
    	
    	public Name(String firstName, String lastName) {
    		this.firstName = firstName;
    		this.lastName = lastName;		
    	}
    	
    	public String getFirstName(){
    		return firstName;
    	}
    	
    	public String getLastName(){
    		return lastName;
    	}
    	
    	public String toString(){
    		return firstName +" "+ lastName;
    	}
    	
    }

F:\java>javac TestCollection.java
    注: TestCollection.java使用了未经检查或不安全的操作。
    注: 有关详细信息, 请使用 -Xlint:unchecked 重新编译。
    
    F:\java>java TestCollection
    3
    [hello, f1 l1, 100]
    
    F:\java>

可以看到上面的信息，出现了一些警告，不用管他。

输出结果为：

\[hello, f1 l1, 100\]

BasicContainer.java

import java.util.*;
    
    public class BasicContainer {
        public static void main(String[] args) {
            Collection c = new HashSet();
            c.add("hello");
            c.add(new Name("f1","l1"));
            c.add(new Integer(100));
            c.remove("hello"); 
            c.remove(new Integer(100));
    		//remove移除容器中的元素
            System.out.println(c.remove(new Name("f1","l1")));
            System.out.println(c);
        }
    
    
    }
    
    class Name /*implements Comparable*/ {
        private String firstName,lastName;
        public Name(String firstName, String lastName) {
            this.firstName = firstName; this.lastName = lastName;
        }
        public String getFirstName() {  return firstName;   }
        public String getLastName() {   return lastName;   }
        public String toString() {  return firstName + " " + lastName;  }
        
    	/*
        public boolean equals(Object obj) {
    	    if (obj instanceof Name) {
    	        Name name = (Name) obj;
    	        return (firstName.equals(name.firstName))
    	            && (lastName.equals(name.lastName));
    	    }
    	    return super.equals(obj);
    		}
    		public int hashCode() {
    		    return firstName.hashCode();
    		}
    		
    		
    		
    		public int compareTo(Object o) {
            Name n = (Name)o;
            int lastCmp = 
                lastName.compareTo(n.lastName);
            return 
                 (lastCmp!=0 ? lastCmp :
                  firstName.compareTo(n.firstName));
        }
    	*/
    		
    }

F:\java>javac BasicContainer.java
    注: BasicContainer.java使用了未经检查或不安全的操作。
    注: 有关详细信息, 请使用 -Xlint:unchecked 重新编译。
    
    F:\java>java BasicContainer
    false
    [f1 l1]
    
    F:\java>

删除不彻底，重写Name类的equlas()和hashCode()方法

BasicContainer.java

import java.util.*;
    
    public class BasicContainer {
        public static void main(String[] args) {
            Collection c = new HashSet();
            c.add("hello");
            c.add(new Name("f1","l1"));
            c.add(new Integer(100));
            c.remove("hello"); 
            c.remove(new Integer(100));
    		//remove移除容器中的元素
            System.out.println(c.remove(new Name("f1","l1")));
            System.out.println(c);
        }
    
    
    }
    
    class Name /*implements Comparable*/ {
        private String firstName,lastName;
        public Name(String firstName, String lastName) {
            this.firstName = firstName; this.lastName = lastName;
        }
        public String getFirstName() {  return firstName;   }
        public String getLastName() {   return lastName;   }
        public String toString() {  return firstName + " " + lastName;  }
        
    	/**
    	*	重写equals方法
    	*/
        public boolean equals(Object obj) {
    	    if (obj instanceof Name) {
    	        Name name = (Name) obj;
    	        return (firstName.equals(name.firstName))
    	            && (lastName.equals(name.lastName));
    	    }
    	    return super.equals(obj);
    	}
    	/**
    	*	重写hashCode方法
    	*/
    	public int hashCode() {
    		    return firstName.hashCode();
    	}
    			
    	/*
    	public int compareTo(Object o) {
            Name n = (Name)o;
            int lastCmp = 
                lastName.compareTo(n.lastName);
            return 
                 (lastCmp!=0 ? lastCmp :
                  firstName.compareTo(n.firstName));
        }
    	*/
    		
    }

F:\java>javac BasicContainer.java
    注: BasicContainer.java使用了未经检查或不安全的操作。
    注: 有关详细信息, 请使用 -Xlint:unchecked 重新编译。
    
    F:\java>java BasicContainer
    true
    []
    
    F:\java>

[f1f3c62a-cdc7-3aba-86ab-11a561f4d305.png]: /images/20220406/0d722b6a0ee64442a7c976a8ec530988.png