68 lines
1.4 KiB
Java
68 lines
1.4 KiB
Java
// streams/OptionalFilter.java
|
|
import java.util.*;
|
|
import java.util.stream.*;
|
|
import java.util.function.*;
|
|
|
|
class OptionalFilter {
|
|
static String[] elements = {
|
|
"Foo", "", "Bar", "Baz", "Bingo"
|
|
};
|
|
static Stream<String> testStream() {
|
|
return Arrays.stream(elements);
|
|
}
|
|
static void test(String descr, Predicate<String> pred) {
|
|
System.out.println(" ---( " + descr + " )---");
|
|
for(int i = 0; i <= elements.length; i++) {
|
|
System.out.println(
|
|
testStream()
|
|
.skip(i)
|
|
.findFirst()
|
|
.filter(pred));
|
|
}
|
|
}
|
|
public static void main(String[] args) {
|
|
test("true", str -> true);
|
|
test("false", str -> false);
|
|
test("str != \"\"", str -> str != "");
|
|
test("str.length() == 3", str -> str.length() == 3);
|
|
test("startsWith(\"B\")", str -> str.startsWith("B"));
|
|
}
|
|
}
|
|
/* Output:
|
|
---( true )---
|
|
Optional[Foo]
|
|
Optional[]
|
|
Optional[Bar]
|
|
Optional[Baz]
|
|
Optional[Bingo]
|
|
Optional.empty
|
|
---( false )---
|
|
Optional.empty
|
|
Optional.empty
|
|
Optional.empty
|
|
Optional.empty
|
|
Optional.empty
|
|
Optional.empty
|
|
---( str != "" )---
|
|
Optional[Foo]
|
|
Optional.empty
|
|
Optional[Bar]
|
|
Optional[Baz]
|
|
Optional[Bingo]
|
|
Optional.empty
|
|
---( str.length() == 3 )---
|
|
Optional[Foo]
|
|
Optional.empty
|
|
Optional[Bar]
|
|
Optional[Baz]
|
|
Optional.empty
|
|
Optional.empty
|
|
---( startsWith("B") )---
|
|
Optional.empty
|
|
Optional.empty
|
|
Optional[Bar]
|
|
Optional[Baz]
|
|
Optional[Bingo]
|
|
Optional.empty
|
|
*/
|