Scala Map retain() 方法及其示例

retain() 方法是用来保留所有满足指定条件的 map 中的键值对。

方法定义：def retain(p: (A, B) => Boolean): Map.this.type

返回类型：返回所有满足指定条件的键值对的 map 。

示例 #1：

// Scala program of retain()
// method
  
// Creating object
object GfG
{ 
  
    // Main method
    def main(args:Array[String])
    {
      
        // Creating a mutable map
        val m1 = scala.collection.mutable.Map(3 -> "geeks", 
                                    1 -> "for", 2 -> "cs")
          
        // Applying retain method
        val result = m1.retain((key,value) => key > 1)
          
        // Displays output
        println(result)
      
    }
}

Map(2 -> cs, 3 -> geeks)

示例 #2：

// Scala program of retain()
// method
  
// Creating object
object GfG
{ 
  
    // Main method
    def main(args:Array[String])
    {
      
        // Creating a mutable map
        val m1 = scala.collection.mutable.Map(3 -> "geeks",
                                    1 -> "for", 1 -> "cs")
          
        // Applying retain method
        val result = m1.retain((key,value) => key > 1)
          
        // Displays output
        println(result)
          
    }
}