Java –将数组转换为ArrayList

川长思鸟来 2023-02-15 05:11 10阅读 0赞

在Java中，我们可以使用`new ArrayList<>(Arrays.asList(array))`将`Array`转换为`ArrayList`

ArrayExample1.java

package com.mkyong;
    
    import java.util.ArrayList;
    import java.util.Arrays;
    import java.util.List;
    
    public class ArrayExample1 {
    
        public static void main(String[] args) {
    
            String[] str = {"A", "B", "C"};
    
            List<String> list = new ArrayList<>(Arrays.asList(str));
    
            list.add("D");
    
            list.forEach(x -> System.out.println(x));
    
        }
    }

输出量

A
    B
    C
    D

`Arrays.asList`返回一个固定的或不可修改的列表，如果我们修改列表，将抛出`UnsupportedOperationException` 。

List<String> list = Arrays.asList(str); 				 // unmodifiable list
    
    	list.add("D"); 		// java.lang.UnsupportedOperationException
    	
    	List<String> list2 = new ArrayList<>(Arrays.asList(str)); // modifiable list
    	
    	list2.add("D"); 	// ok

## 1. Java 8流 ##

ArrayExample2.java

package com.mkyong;
    
    import java.util.ArrayList;
    import java.util.List;
    import java.util.stream.Collectors;
    import java.util.stream.Stream;
    
    public class ArrayExample2 {
    
        public static void main(String[] args) {
    
            String[] str = {"A", "B", "C"};
    
            ArrayList<String> list1 = Stream.of(str).collect(Collectors.toCollection(ArrayList::new));
            list1.add("D");
            list1.forEach(x -> System.out.println(x));
    
            List<String> list2 = Stream.of(str).collect(Collectors.toList());
            list2.add("D");
            list2.forEach(x -> System.out.println(x));
    
        }
    }

输出量

A
    B
    C
    D
    A
    B
    C
    D

## 2. Java 9 – List.of（） ##

*PS `List.of`返回固定或不可修改的列表*

ArrayExample3.java

package com.mkyong;
    
    import java.util.ArrayList;
    import java.util.List;
    
    public class ArrayExample3 {
    
        public static void main(String[] args) {
    
            String[] str = {"A", "B", "C"};
    
            // Java 9
            List<String> list = new ArrayList<>(List.of("A", "B", "C"));
    
            list.add("D");
    
            list.forEach(x -> System.out.println(x));
    
        }
    }

输出量

A
    B
    C
    D

## 参考文献 ##

*  Java清单java.lang.UnsupportedOperationException
 *  [Java 9清单][Java 9]

标签： [数组][Link 1] [转换][Link 2] [Java][] [Java 8][] [Java 9][Java 9 1]

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[Java 9]: https://docs.oracle.com/javase/9/docs/api/java/util/List.html#of--
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