在Java中将字符串集合转换为字符串数组

给定一组字符串，任务是将 Set 转换为Java中的字符串数组。

例子：

Input: Set: ["ForGeeks", "A Computer Portal", "Geeks"]
Output: String[]: ["ForGeeks", "A Computer Portal", "Geeks"]

Input: Set: ["G", "e", "k", "s"]
Output: String[]: ["G", "e", "k", "s"]

方法1：朴素方法。

获取字符串集。
创建一个空的字符串数组，其大小与字符串集的大小相同。
使用高级 for 循环，将字符串集合的每个元素复制到字符串数组中。
返回或打印字符串数组。

下面是上述方法的实现：

// Java program to convert
// Set of Strings to Array of Strings
  
import java.util.Arrays;
import java.util.Set;
import java.util.HashSet;
  
class GFG {
  
    // Function to convert Set to String[]
    public static String[] convert(Set setOfString)
    {
  
        // Create String[] of size of setOfString
        String[] arrayOfString = new String[setOfString.size()];
  
        // Copy elements from set to string array
        // using advanced for loop
        int index = 0;
        for (String str : setOfString)
            arrayOfString[index++] = str;
  
        // return the formed String[]
        return arrayOfString;
    }
  
    public static void main(String[] args)
    {
  
        // Get the Set of String
        Set
            setOfString = new HashSet<>(
                Arrays.asList("Geeks",
                              "ForGeeks",
                              "A Computer Portal"));
  
        // Print the setOfString
        System.out.println("Set of String: "
                           + setOfString);
  
        // Convert Set to String array
        String[] arrayOfString = convert(setOfString);
  
        // Print the arrayOfString
        System.out.println("Array of String: "
                           + Arrays.toString(arrayOfString));
    }
}

输出：

Set of String: [ForGeeks, A Computer Portal, Geeks]
Array of String: [ForGeeks, A Computer Portal, Geeks]

方法 2 ：使用 Set.toArray() 方法。

获取字符串集。
使用 Set.toArray() 方法通过传递一个字符串将字符串集合转换为字符串数组
String 类型的空数组。 JVM 将为字符串数组分配内存。
返回或打印字符串数组。

下面是上述方法的实现：

// Java program to convert
// Set of Strings to Array of Strings
  
import java.util.Arrays;
import java.util.Set;
import java.util.HashSet;
  
class GFG {
  
    // Function to convert Set to String[]
    public static String[] convert(Set setOfString)
    {
  
        // Create String[]  from setOfString
        String[] arrayOfString = setOfString
                                     .toArray(new String[0]);
  
        // return the formed String[]
        return arrayOfString;
    }
  
    public static void main(String[] args)
    {
  
        // Get the Set of String
        Set
            setOfString = new HashSet<>(
                Arrays.asList("Geeks",
                              "ForGeeks",
                              "A Computer Portal"));
  
        // Print the setOfString
        System.out.println("Set of String: "
                           + setOfString);
  
        // Convert Set to String array
        String[] arrayOfString = convert(setOfString);
  
        // Print the arrayOfString
        System.out.println("Array of String: "
                           + Arrays.toString(arrayOfString));
    }
}

输出：

Set of String: [ForGeeks, A Computer Portal, Geeks]
Array of String: [ForGeeks, A Computer Portal, Geeks]

方法 3 ：使用 Arrays.copyOf() 方法。

获取字符串集。
使用 Arrays.copyOf() 方法将字符串集合转换为字符串数组，方法是将字符串集合、字符串集合的大小和所需的输出类型作为字符串 [] 传递。
返回或打印字符串数组。

下面是上述方法的实现：

// Java program to convert
// Set of Strings to Array of Strings
  
import java.util.Arrays;
import java.util.Set;
import java.util.HashSet;
  
class GFG {
  
    // Function to convert Set to String[]
    public static String[] convert(Set setOfString)
    {
  
        // Create String[]  from setOfString
        String[] arrayOfString = Arrays
                                     .copyOf(
                                         setOfString.toArray(),
                                         setOfString.size(),
                                         String[].class);
  
        // return the formed String[]
        return arrayOfString;
    }
  
    public static void main(String[] args)
    {
  
        // Get the Set of String
        Set
            setOfString = new HashSet<>(
                Arrays.asList("Geeks",
                              "ForGeeks",
                              "A Computer Portal"));
  
        // Print the setOfString
        System.out.println("Set of String: "
                           + setOfString);
  
        // Convert Set to String array
        String[] arrayOfString = convert(setOfString);
  
        // Print the arrayOfString
        System.out.println("Array of String: "
                           + Arrays.toString(arrayOfString));
    }
}

输出：

Set of String: [ForGeeks, A Computer Portal, Geeks]
Array of String: [ForGeeks, A Computer Portal, Geeks]

方法 4 ：使用 System.arraycopy() 方法。

获取字符串集。
使用 System.arraycopy() 方法将字符串集合转换为字符串数组。
返回或打印字符串数组。

下面是上述方法的实现：

// Java program to convert
// Set of Strings to Array of Strings
  
import java.util.Arrays;
import java.util.Set;
import java.util.HashSet;
  
class GFG {
  
    // Function to convert Set to String[]
    public static String[] convert(Set setOfString)
    {
  
        // Create String[] of size of setOfString
        String[] arrayOfString = new String[setOfString.size()];
  
        // Convert setOfString to String[]
        System.arraycopy(
            // source
            setOfString.toArray(),
  
            // from index to be copied from Source
            0,
  
            // Destination
            arrayOfString,
  
            // From index where to be copied in Destination
            0,
  
            // Number of elements to be copied
            setOfString.size());
  
        // return the formed String[]
        return arrayOfString;
    }
  
    public static void main(String[] args)
    {
  
        // Get the Set of String
        Set
            setOfString = new HashSet<>(
                Arrays.asList("Geeks",
                              "ForGeeks",
                              "A Computer Portal"));
  
        // Print the setOfString
        System.out.println("Set of String: "
                           + setOfString);
  
        // Convert Set to String array
        String[] arrayOfString = convert(setOfString);
  
        // Print the arrayOfString
        System.out.println("Array of String: "
                           + Arrays.toString(arrayOfString));
    }
}

输出：

Set of String: [ForGeeks, A Computer Portal, Geeks]
Array of String: [ForGeeks, A Computer Portal, Geeks]

方法 5 ：使用Java 8 流。

获取字符串集。
将字符串集转换为流使用流（）方法。
转换流使用 toArray() 方法到 String[]。
返回或打印字符串数组。

下面是上述方法的实现：

// Java program to convert
// Set of Strings to Array of Strings
  
import java.util.Arrays;
import java.util.Set;
import java.util.HashSet;
  
class GFG {
  
    // Function to convert Set to String[]
    public static String[] convert(Set setOfString)
    {
  
        // Create String[] from setOfString
        String[] arrayOfString = setOfString
  
                                     // Convert Set of String
                                     // to Stream
                                     .stream()
  
                                     // Convert Stream
                                     // to String[]
                                     .toArray(String[] ::new);
  
        // return the formed String[]
        return arrayOfString;
    }
  
    public static void main(String[] args)
    {
  
        // Get the Set of String
        Set
            setOfString = new HashSet<>(
                Arrays.asList("Geeks",
                              "ForGeeks",
                              "A Computer Portal"));
  
        // Print the setOfString
        System.out.println("Set of String: "
                           + setOfString);
  
        // Convert Set to String array
        String[] arrayOfString = convert(setOfString);
  
        // Print the arrayOfString
        System.out.println("Array of String: "
                           + Arrays.toString(arrayOfString));
    }
}

输出：

Set of String: [ForGeeks, A Computer Portal, Geeks]
Array of String: [ForGeeks, A Computer Portal, Geeks]