java容器之Iterator(迭代器)

梦里梦外; 2022-04-06 09:40 250阅读 0赞

# java容器之Iterator(迭代器) #

### Method Summary ###

<table style="font-size:14px;width:571px;border-left:1px solid #eeeeee;border-right:1px solid #eeeeee;border-bottom:1px solid #eeeeee;color:#353833;font-family:'DejaVu Sans', Arial, Helvetica, sans-serif;"> 
 <tbody> 
  <tr style="background-color:#eeeeef;"> 
   <td style="vertical-align:top;font-size:13px;width:132px;"><code style="font-family:'DejaVu Sans Mono', monospace;font-size:14px;line-height:1.4em;">boolean</code></td> 
   <td style="vertical-align:top;font-size:13px;"> <code style="font-family:'DejaVu Sans Mono', monospace;font-size:14px;line-height:1.4em;"><span style="font-weight:bold;"><a style="color:#4a6782;" rel="nofollow">hasNext</a></span>()</code> 
    <div style="color:#474747;font-size:14px;font-family:'DejaVu Serif', Georgia, 'Times New Roman', Times, serif;">
      Returns&nbsp; 
     <code style="font-family:'DejaVu Sans Mono', monospace;font-size:14px;line-height:1.4em;">true</code>&nbsp;if the iteration has more elements. 
    </div> 
    <div style="color:#474747;font-size:14px;font-family:'DejaVu Serif', Georgia, 'Times New Roman', Times, serif;">
      判断游标右边是否有元素 
    </div> </td> 
  </tr> 
  <tr> 
   <td style="vertical-align:top;font-size:13px;width:132px;"><code style="font-family:'DejaVu Sans Mono', monospace;font-size:14px;line-height:1.4em;"><a style="color:#4a6782;font-weight:bold;" title="type parameter in Iterator" rel="nofollow">E</a></code></td> 
   <td style="vertical-align:top;font-size:13px;"> <code style="font-family:'DejaVu Sans Mono', monospace;font-size:14px;line-height:1.4em;"><span style="font-weight:bold;"><a style="color:#4a6782;" rel="nofollow">next</a></span>()</code> 
    <div style="color:#474747;font-size:14px;font-family:'DejaVu Serif', Georgia, 'Times New Roman', Times, serif;">
      Returns the next element in the iteration. 
    </div> 
    <div style="color:#474747;font-size:14px;font-family:'DejaVu Serif', Georgia, 'Times New Roman', Times, serif;">
      返回游标右边的元素，并将游标移动到下一位置 
    </div> </td> 
  </tr> 
  <tr style="background-color:#eeeeef;"> 
   <td style="vertical-align:top;font-size:13px;width:132px;"><code style="font-family:'DejaVu Sans Mono', monospace;font-size:14px;line-height:1.4em;">default void</code></td> 
   <td style="vertical-align:top;font-size:13px;"> <code style="font-family:'DejaVu Sans Mono', monospace;font-size:14px;line-height:1.4em;"><span style="font-weight:bold;"><a style="color:#4a6782;" rel="nofollow">remove</a></span>()</code> 
    <div style="color:#474747;font-size:14px;font-family:'DejaVu Serif', Georgia, 'Times New Roman', Times, serif;">
      Removes from the underlying collection the last element returned by this iterator (optional operation). 
    </div> 
    <div style="color:#474747;font-size:14px;font-family:'DejaVu Serif', Georgia, 'Times New Roman', Times, serif;">
      删除游标左边的元素 
    </div> </td> 
  </tr> 
 </tbody> 
</table>

TestIterator.java

import java.util.*;
    
    //Iterator迭代器测试
    public class TestIterator {
        public static void main(String[] args) {
            Collection c = new HashSet();
            c.add(new Name("f1","l1"));
    		c.add(new Name("f2","l2"));
    		c.add(new Name("f3","l3"));
    		Iterator i = c.iterator();
    		
    		//判断游标右边是否有元素
    		while(i.hasNext()){
    			//next()的返回值要强制转换为对应的对象类型
    			Name n = (Name)i.next();
    			System.out.println(n.getFirstName() + " ");
    		}
    		System.out.println();
    		
    		///
    		
    		Collection c2 = new HashSet();
            c2.add(new Name("f1111","l1111"));
    		c2.add(new Name("f2","l2"));
    		c2.add(new Name("f3333","l3333"));
    		
    		for(Iterator it = c2.iterator(); it.hasNext();){
    			Name name = (Name)it.next();
    			if(name.getFirstName().length() < 3){
    				it.remove();
    				//如果换成c.remove(name)会产生例外
    			}
    		}
    		System.out.println(c2);//[f1111 l1111, f3333 l3333]
    		
        }
    
    
    }
    
    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();
    	}
    		
    }

F:\java>javac TestIterator.java
    注: TestIterator.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 TestIterator
    f1
    f2
    f3
    
    [f1111 l1111, f3333 l3333]
    
    F:\java>