Properties類的containsKey(value)方法用于檢查此Properties對象是否包含此Key的任何映射(對于其中存在的任何鍵)。它将此值作為參數進行比較,并傳回一個布爾值作為結果。
用法:
public Object containsKey(Object value)
參數:此方法接受參數值,該參數值是要在此屬性中搜尋的鍵。
傳回值:此方法傳回一個布爾值,該布爾值說明此鍵是否存在于此Properties對象中的結果。
以下示例程式旨在說明containsKey(value)方法:
示例1:
// Java program to demonstrate
// containsKey(value) method.
import java.util.*;
public class GFG {
// Main method
public static void main(String[] args)
{
// Create a properties and add some values
Properties properties = new Properties();
properties.put("Pen", 10);
properties.put("Book", 500);
properties.put("Clothes", 400);
properties.put("Mobile", 5000);
// Print Properties details
System.out.println("Current Properties: "
+ properties.toString());
// Check if Pen is present or not
// using containsKey()
System.out.println("Is Pen present: "
+ properties.containsKey("Pen"));
}
}
輸出:
Current Properties: {Book=500, Mobile=5000, Pen=10, Clothes=400}
Is Pen present: true
示例2:
// Java program to demonstrate
// containsKey(value) method.
import java.util.*;
public class GFG {
// Main method
public static void main(String[] args)
{
// Create a properties and add some values
Properties properties = new Properties();
properties.put(1, "100RS");
properties.put(2, "500RS");
properties.put(3, "1000RS");
// print Properties details
System.out.println("Current Properties: "
+ properties.toString());
// Check if 5 is present or not
// using containsKey()
System.out.println("Is 5 present: "
+ properties.containsKey(5));
}
}
輸出:
Current Properties: {3=1000RS, 2=500RS, 1=100RS}
Is 5 present: false
參考:https://docs.oracle.com/javase/9/docs/api/java/util/Properties.html#containsKey-java.lang.Object-