• 主頁
  • 文章
  • 一般的
  • 在 Java 中，如何在迭代列表、ArrayList 時刪除元素？ （5種不同的方式）

在 Java 中，如何在迭代列表、ArrayList 時刪除元素？ （5種不同的方式）

已發表: 2021-11-08
在 Java 中，如何在迭代列表、ArrayList 時刪除元素？ （5種不同的方式）

在Java中如何在迭代時從ArrayList中刪除元素？ 如果在迭代 ArrayList 時從 ArrayList 中刪除項目，list.remove(s) 將拋出 java.util.ConcurrentModificationException。

讓我們開始吧。

創建類：CrunchifyRemoveItemFromList.java

我們將使用以下5 methods在迭代時從 ArrayList 中刪除一個元素。

  • 方法一：collectionRemoveIf 方法
  • 方法二：collectionRemoveIfObjectEquals 方法
  • 方法三：collectiontereratorRemove 方法
  • 方法四：listIteratorWayToRemoveElement 方法
  • 方法五：streamFilterCollectWay 方法

複製以下代碼並保存。

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
package crunchify . com . java . tutorials ;
 
import java . util . ArrayList ;
import java . util . List ;
import java . util . ListIterator ;
import java . util . Objects ;
import java . util . stream . Collectors ;
 
/**
* @author Crunchify.com
* In Java How to remove Elements while Iterating a List? (5 different ways to remove items)
*/
 
public class CrunchifyRemoveItemFromList {
 
     public static void main ( String [ ] args ) {
 
         collectionRemoveIfMethod ( ) ;
         collectionRemoveIfObjectEqualsMethod ( ) ;
         collectionteratorRemoveMethod ( ) ;
         listIteratorWayToRemoveElement ( ) ;
         streamFilterCollectWay ( ) ;
 
     }
 
     // Method-1: collectionRemoveIfMethod to remove elements from ArrayList
     private static void collectionRemoveIfMethod ( ) {
         List < String > crunchifyList = new ArrayList < > ( ) ;
         crunchifyList . add ( "Google.com" ) ;
         crunchifyList . add ( "Crunchify.com" ) ;
         crunchifyList . add ( "Facebook.com" ) ;
         crunchifyList . add ( "Apple.com" ) ;
 
         // removeIf(): Removes all of the elements of this collection that satisfy the given predicate.
         // Errors or runtime exceptions thrown during iteration or by the predicate are relayed to the caller.
         crunchifyList . removeIf ( "Apple.com" : : equals ) ;
 
         // equals(): Compares this string to the specified object.
         // The result is true if and only if the argument is not null and is a
         // String object that represents the same sequence of characters as this object.
         // For finer-grained String comparison, refer to java.text.Collator.
 
         System . out . print ( "Method-1 Result: " ) ;
         crunchifyPrint ( crunchifyList ) ;
     }
 
     // Simple print function
     private static void crunchifyPrint ( List < String > crunchifyList ) {
 
         System . out . println ( crunchifyList ) ;
     }
 
     // Method-2: collectionRemoveIfObjectEqualsMethod to remove elements from ArrayList
     private static void collectionRemoveIfObjectEqualsMethod ( ) {
         List < String > crunchifyList = new ArrayList < > ( ) ;
         crunchifyList . add ( "Google.com" ) ;
         crunchifyList . add ( "Crunchify.com" ) ;
         crunchifyList . add ( "Facebook.com" ) ;
         crunchifyList . add ( "Apple.com" ) ;
 
         // removeIf() Params:
         // filter – a predicate which returns true for elements to be removed
         // Returns:
         // true if any elements were removed
         // Throws:
         // NullPointerException – if the specified filter is null
         crunchifyList . removeIf ( crunchify - >
                 Objects . equals ( crunchify ,
                         "Crunchify.com" ) | |
                         Objects . equals ( crunchify , "Apple.com" ) ) ;
 
         System . out . print ( "Method-2 Result: " ) ;
         crunchifyPrint ( crunchifyList ) ;
     }
 
     // Method-3: collectionteratorRemoveMethod to remove elements from ArrayList
     private static void collectionteratorRemoveMethod ( ) {
         List < String > crunchifyList = new ArrayList < > ( ) ;
         crunchifyList . add ( "Google.com" ) ;
         crunchifyList . add ( "Crunchify.com" ) ;
         crunchifyList . add ( "Facebook.com" ) ;
         crunchifyList . add ( "Apple.com" ) ;
 
         // listIterator(): Returns a list iterator over the elements in this list (in proper sequence).
         ListIterator < String > crunchifyIterator = crunchifyList . listIterator ( ) ;
 
         // hasNext(): Returns true if this list iterator has more elements when traversing the list in the forward direction.
         // (In other words, returns true if next would return an element rather than throwing an exception.)
         while ( crunchifyIterator . hasNext ( ) ) {
 
             // equals(): Compares this string to the specified object.
             // The result is true if and only if the argument is not null and is a
             // String object that represents the same sequence of characters as this object.
             //For finer-grained String comparison, refer to java.text.Collator.
             if ( "Crunchify.com" . equals ( crunchifyIterator . next ( ) ) ) {
                 // next(): returns the next element in the list and advances the cursor position.
                 // This method may be called repeatedly to iterate through the list, or intermixed with calls to previous to go back and forth.
                 // (Note that alternating calls to next and previous will return the same element repeatedly.)
 
                 crunchifyIterator . remove ( ) ;
                 // remove(): Removes from the list the last element that was returned by next or previous (optional operation).
                 // This call can only be made once per call to next or previous. It can be made only if add has not been called after the last call to next or previous.
             }
         }
 
         System . out . print ( "Method-3 Result: " ) ;
         crunchifyPrint ( crunchifyList ) ;
     }
 
     // Method-4: listIteratorWayToRemoveElement to remove elements from ArrayList
     private static void listIteratorWayToRemoveElement ( ) {
         List < String > crunchifyList = new ArrayList < > ( ) ;
         crunchifyList . add ( "Google.com" ) ;
         crunchifyList . add ( "Crunchify.com" ) ;
         crunchifyList . add ( "Facebook.com" ) ;
         crunchifyList . add ( "Apple.com" ) ;
 
         List < String > crunchifyNewList = new ArrayList < > ( ) ;
         for ( String s : crunchifyList ) {
             if ( ! "Facebook.com" . equals ( s ) ) {
                 crunchifyNewList . add ( s ) ;
             }
         }
 
         System . out . print ( "Method-4 Result: " ) ;
         crunchifyPrint ( crunchifyNewList ) ;
     }
 
     // Method-5: streamFilterCollectWay to remove elements from ArrayList
     private static void streamFilterCollectWay ( ) {
 
         List < String > crunchifyList = new ArrayList < > ( ) ;
         crunchifyList . add ( "Google.com" ) ;
         crunchifyList . add ( "Crunchify.com" ) ;
         crunchifyList . add ( "Facebook.com" ) ;
         crunchifyList . add ( "Apple.com" ) ;
 
         // stream(): Returns a sequential Stream with this collection as its source.
         // This method should be overridden when the spliterator() method cannot return a spliterator
         // that is IMMUTABLE, CONCURRENT, or late-binding. (See spliterator() for details.)
 
         // filer(): Returns a stream consisting of the elements of this stream that match the given predicate.
         // This is an intermediate operation.
         List < String > crunchifyNewList = crunchifyList .
                 stream ( ) .
                 filter ( crunchify - > ! "Crunchify.com" .
                         equals ( crunchify ) )
                 . collect ( Collectors . toList ( ) ) ;
 
         // toList(): Returns a Collector that accumulates the input elements into a new List.
         // There are no guarantees on the type, mutability, serializability, or thread-safety of the List returned;
         // if more control over the returned List is required, use toCollection(Supplier).
 
         System . out . print ( "Method-5 Result: " ) ;
         crunchifyPrint ( crunchifyNewList ) ;
     }
 
}

只需將上述程序作為 Java 應用程序運行，您將看到如下結果。 您不會看到並發修改異常。

這是 java.util.Collection.removeIf() 方法：

java.util.Collection removeIf 函數

IntelliJ IDEA 控制台結果：

去年我們從 Eclipse 遷移到 IntelliJ IDEA，我們非常喜歡它。 這是控制台結果。

1
2
3
4
5
6
7
8
9
/ Users / app / Library / Java / JavaVirtualMachines / openjdk - 17.0.1 / Contents / Home / bin / java -- enable - preview - javaagent : / Applications / IntelliJ IDEA . app / Contents / lib / idea_rt . jar crunchify . com . java . tutorials . CrunchifyRemoveItemFromList
Method - 1 Result : [ Google . com , Crunchify . com , Facebook . com ]
Method - 2 Result : [ Google . com , Facebook . com ]
Method - 3 Result : [ Google . com , Facebook . com , Apple . com ]
Method - 4 Result : [ Google . com , Crunchify . com , Apple . com ]
Method - 5 Result : [ Google . com , Facebook . com , Apple . com ]
 
Process finished with exit code 0
 

如果您在運行此 Java 程序時遇到任何問題，請告訴我。