小溪。Java 中的 Builder add()方法
原文:https://www . geesforgeks . org/stream-builder-add-method-in-Java/
小溪。Builder add(T t) 用于在流的构建阶段将元素插入到元素中。它向正在构建的流中添加一个元素。
语法:
default Stream.Builder<T> add(T t)
参数:此方法添加一个强制参数 t ，它是要输入到流中的元素。
异常:当构建器已经转换到构建状态时，该方法抛出illegalstatexception:。这意味着该流已经进入构建阶段，现在不能更改。因此，没有更多的元素可以添加到流中。
以下是说明 add()方法的示例:
例 1:
// Java code to show the implementation
// of Stream.Builder add(T t)
import java.util.stream.Stream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Declaring an empty Stream
Stream.Builder<String> str_b = Stream.builder();
// Inserting elements into the stream
// using Stream.Builder add(T t)
str_b.add("Geeks");
str_b.add("for");
str_b.add("GeeksforGeeks");
str_b.add("Data Structures");
str_b.add("Geeks Classes");
// Creating the String Stream
// The stream has now entered the built phase
Stream<String> s = str_b.build();
// printing the elements
System.out.println("Stream successfully built");
s.forEach(System.out::println);
}
}
Output:
Stream successfully built
Geeks
for
GeeksforGeeks
Data Structures
Geeks Classes
示例 2: 说明 IllegalStateException
// Java code to show the implementation
// of Stream.Builder add(T t)
import java.util.stream.Stream;
class GFG {
// Driver code
public static void main(String[] args)
{
// Declaring an empty Stream
Stream.Builder<String> str_b = Stream.builder();
// using Stream.Builder add(T t)
str_b.add("5");
str_b.add("6");
str_b.add("7");
str_b.add("8");
str_b.add("9");
// Creating the String Stream
// The stream has now entered the built phase
Stream<String> s = str_b.build();
// printing the elements
System.out.println("Stream successfully built");
s.forEach(System.out::println);
// Trying to add another element into the stream
// Since the Stream is in built phase
// This operation is not possible now
// Hence add() will throw exception now
try {
str_b.add("50");
}
catch (Exception e) {
System.out.println("Exception thrown "
+ "when now adding element into the stream: "
+ e);
}
}
}
Output:
Stream successfully built
5
6
7
8
9
Exception thrown when now adding element into the stream: java.lang.IllegalStateException
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