Arrays.asList method summary

Without further ado, look at the code:

import java.util.Arrays; 
import java.util.List; 
/** 
 * 
 *  This class demonstrates Arrays In the class asList methods  
 *  through 4 Let's do it in paragraphs , The characteristics of this method are shown . 
 * 
 * (1)  This method does not support arrays of basic data types well , It is not recommended when an array is a primitive data type  
 * (2)  When using asList() Method, the array is linked to the list 1 the . 
 *    When updating one of them 1 , the other 1 Four will be updated automatically.  
 *    Pay attention to : Only for object array types , Arrays of basic data types do not have this feature  
 * (3) asList The array you get is none add and remove methods  
 * 
 *  Read the relevant : By looking at the Arrays The source of the class can be known ,asList The returned List is Array Implemented in  
 *  The inner class , This class is not defined add and remove methods . In addition , Why change it 1 a , On the other 1 An automatic also  
 *  It's updated , because asList To obtain List The actual reference is to the array  
 */ 
public class AsListTest {  
  public static void main(String[] args) { 
    /*  The paragraph 1: Basic data type usage asList The problems in the  */ 
    /*  instructions : Although the JDK1.6 Is able to convert an array of basic data types into List, But there is a catch  */ 
    int[] a_int = { 1, 2, 3, 4 }; 
    /*  The expected output should be 1,2,3,4, But the actual output is just 1 A reference ,  Here it a_int As a 1 An element  */ 
    List a_int_List = Arrays.asList(a_int); 
    foreach(a_int_List); 
    /*  To do that we need to go through the elements like this  */ 
    foreachForBase(a_int_List);  
    /*  The paragraph 2: Use of an array of object types asList, That's what we expected  */ 
    Integer[] a_Integer = new Integer[] { 1, 2, 3, 4 }; 
    List a_Integer_List = Arrays.asList(a_Integer); 
    foreach(a_Integer_List);  
    /*  The paragraph 3: When updating an array or asList After the List, On the other 1 Four will be updated automatically  */ 
    a_Integer_List.set(0, 0); 
    foreach(a_Integer_List); 
    foreach(a_Integer); 
    a_Integer[0] = 5; 
    foreach(a_Integer_List); 
    foreach(a_Integer); 
    /*  The paragraph 4: Array of primitive types , through asList After the List After the corresponding value is modified , An exception is reported at run time  
     *  But the array of primitive types corresponds to List It's going to change , There is no doubt about it  
     */    
    /* 
     * a_int_List.set(0, 0); 
     * foreach(a_int_List); foreach(a_int); 
     */ 
    a_int[0] = 5; 
    foreachForBase(a_int_List); 
    foreach(a_int); 
  } 
  /*  Printing method  */ 
  private static void foreach(List list) { 
    for (Object object : list) { 
      System.out.print(object + " "); 
    } 
    System.out.println(); 
  } 
  private static void foreachForBase(List a_int_List) { 
    int[] _a_int = (int[]) a_int_List.get(0); 
    foreach(_a_int); 
  } 
  private static void foreach(int[] a_int) { 
    for (int i : a_int) { 
      System.out.print(i + " "); 
    } 
    System.out.println(); 
  } 
  private static void foreach(Integer[] _a_Integer) { 
    for (int i : _a_Integer) { 
      System.out.print(i + " "); 
    } 
    System.out.println(); 
  } 
}