Java Vector firstElement()
Java Vector类的
firstElement()方法用于获取第一个元素(在索引0处)
语法:
以下是
firstElement()方法的声明:
参数:
此方法不接受任何参数。
返回:
firstElement()方法返回正在使用的向量的第一个分量。
异常:
NoSuchElementException -如果向量的元素为空，则此方法引发异常。
兼容性版本:
Java 1.2及更高版本
示例1:
import java.util.*;
public class VectorFirstElementExample1 {
public static void main(String arg[]) {
//Create an empty vector
Vector<Integer> vec = new Vector<>();
//Add element in the vector
vec.add(91);
vec.add(21);
vec.add(31);
vec.add(41);
vec.add(51);
//Get the first element
System.out.println("First element of the vector is = "+vec.firstElement());
}
}
输出:
First element of the vector is = 91
示例2:
import java.util.*;
public class VectorFirstElementExample2 {
public static void main(String arg[]) {
//Create an empty vector
Vector < String > colors = new Vector < String > ();
//Add elements in the vector
colors.add("White");
colors.add("Green");
colors.add("Black");
colors.add("Pink");
//Get the element at specified index
System.out.println("First color of this vector = " +colors.firstElement());
}
}
输出:
First color of this vector = White
示例3:
import java.util.*;
public class VectorFirstElementExample3 {
public static void main(String arg[]) {
//Create an empty vector
Vector<Integer> vecObject = new Vector<Integer>();
//Get the element at specified index
System.out.println("First element of the vector = "+vecObject.firstElement());
}
}
输出:
Exception in thread "main" java.util.NoSuchElementException
at java.base/java.util.Vector.firstElement(Vector.java:511)
at myPackage.VectorFirstElementExample3.main(VectorFirstElementExample3.java:8)
