Java中的Java .lang.String.copyValueOf()

copyValueOf() 主要将字符数组的内容复制到字符串中。此函数有两种可用的变体，本文将讨论这两种变体。
实施1：

Syntax:
public static String copyValueOf(char[] ch)
Parameters:
ch : The character array.
Return Value : 
This function returns the string with the contents of character array copied 

// Java code to demonstrate the working of 
// copyValueOf implementation 1 
public class Copy1 {
  public static void main(String args[]) {
        
    // Initialising Character array
     char[] ch = {'A', 's', 't', 'h', 'a', ' ', 'T', 'y', 'a', 'g', 'i'};
       
     // Initialising String
     String ch2 = "";
       
     // Copying value in ch2
     // now ch2 is equal to "Astha Tyagi"
     ch2 = ch2.copyValueOf( ch );
       
     // Printing String
     System.out.println("The new copied string is : " + ch2);
  }
}

输出：

The new copied string is : Astha Tyagi

在第二种实现中，也可以提取子数组而不是整个数组。
实施2：

Syntax:
public static String copyValueOf(char[] ch, int index, int num)
Parameters:
ch : The character array.
index :  The starting position of array from which copy is to start.
num :  Number of elements that has to be copied. 
Return Value : 
This function returns the string with the contents of character array copied

// Java code to demonstrate the working of 
// copyValueOf implementation 2
public class Copy2 {
  public static void main(String args[]) {
        
    // Initialising Character array
     char[] ch = {'A', 's', 't', 'h', 'a', ' ', 'T', 'y', 'a', 'g', 'i'};
       
     // Initialising String
     String ch2 = "";
       
     // Copying value in ch2
     // only first 5 are extracted
     // now ch2 is equal to "Astha"
     ch2 = ch2.copyValueOf( ch , 0, 5 );
       
     // Printing String
     System.out.println("The new copied string is : " + ch2);
  }
}

输出 ：

The new copied string is : Astha

可能的应用：此函数可用于使用实现 2 从字符串中一般复制或仅提取前缀或后缀。一个可能的示例可以是仅从处理面额的给定“Rs 1000”类型的字符串中提取金额。

// Java code to demonstrate the application of 
// copyValueOf 
public class Appli2 {
  public static void main(String args[]) {
        
    // Initialising Character array
     char[] ch = {'R', 's', ' ', '1', '0', '2', '4' };
       
     // Original array
     System.out.print("The original array is : ");
     for (int i=0; i< ch.length ; i++) 
     System.out.print(ch[i]);
       
      System.out.print("\n");
       
     // Initialising String
     String ch2 = "";
       
     // Copying value in ch2
     // Rs is not included
     // now ch2 is equal to "1024"
     ch2 = ch2.copyValueOf( ch , 3, 4 );
       
     // Printing String
     System.out.println("The new string is : " + ch2);
  }
}

输出 ：

The original array is : Rs 1024
The new string is : 1024