Java Provider get()用法及代碼示例

java.security.Provider類的get()方法用於返回指定鍵所映射的值；如果此映射不包含該鍵的映射，則返回null。

更正式地說，如果此映射包含從鍵k到值v的映射，使得(key.equals(k))，則此方法返回v；否則，此方法返回v。否則返回null。 (最多可以有一個這樣的映射。)

用法:

public Object get(Object key)

參數：此方法將鍵作為要返回其關聯值的參數。

返回值：此方法返回指定鍵映射到的值；如果此映射不包含鍵的映射，則返回null。

下麵是說明get()方法的示例：

示例1:

// Java program to demonstrate 
// get() method 
  
import java.security.*; 
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) throws Exception 
    { 
        // Declaring int values 
        int i = 10, j = 10; 
  
        try { 
            // creating the object of  KeyPairGenerator 
            KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA", "SUN"); 
  
            // getting the Provider of the KeyPairGenerator sr 
            // by using method getProvider() 
            Provider provider = sr.getProvider(); 
  
            // Declaring the variable of set<Map> type 
            Set<Object> set; 
  
            // getting unmodifiable Set view of the property entries 
            set = provider.keySet(); 
  
            // Creating the object of iterator to iterate set 
            Iterator iter = set.iterator(); 
  
            while (i > 0) { 
  
                // getting the mapped value in element 
                // using get() method 
                Object element = provider.get(iter.next()); 
  
                // printing the mapped value 
                System.out.println("value is : " + element); 
                i--; 
            } 
        } 
  
        catch (NoSuchAlgorithmException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

輸出：

value is : SHA1withDSA
value is : SHA1withDSA
value is : SHA1withDSA
value is : Software
value is : sun.security.provider.JavaKeyStore$DualFormatJKS
value is : SHA
value is : sun.security.provider.SHA
value is : sun.security.provider.JavaKeyStore$CaseExactJKS
value is : Software
value is : sun.security.provider.DSA$SHA256withDSA

示例2:

// Java program to demonstrate 
// get() method 
  
import java.security.*; 
import java.util.*; 
  
public class GFG1 { 
    public static void main(String[] argv) throws Exception 
    { 
  
        try { 
            // creating the object of  KeyPairGenerator 
            KeyPairGenerator sr = KeyPairGenerator.getInstance("DSA", "SUN"); 
  
            // getting the Provider of the KeyPairGenerator sr 
            // by using method getProvider() 
            Provider provider = sr.getProvider(); 
  
            // getting the mapped value in element 
            // using get() method 
            System.out.println("Trying to get the value of an unmapped key"); 
            Object element = provider.get("geeks"); 
  
            // printing the mapped value 
            System.out.println("value is : " + element); 
        } 
  
        catch (NoSuchAlgorithmException e) { 
  
            System.out.println("Exception thrown : " + e); 
        } 
    } 
}

輸出：

Trying to get the value of an unmapped key
value is : null

相關用法

注：本文由純淨天空篩選整理自RohitPrasad3大神的英文原創作品 Provider get() method in Java with Examples。非經特殊聲明，原始代碼版權歸原作者所有，本譯文未經允許或授權，請勿轉載或複製。