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[JAVA-22519] Created new module libraries-stream and added 5 articles (#15403)

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This commit is contained in:
panos-kakos
2023-12-13 09:40:13 +02:00
committed by GitHub
parent 0323a8168c
commit 8daf19c9ec
92 changed files with 718 additions and 430 deletions
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libraries/src/test/java/com/baeldung/javassist/JavasisstUnitTest.java
-122
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@@ -1,122 +0,0 @@
package com.baeldung.javassist;
import javassist.CannotCompileException;
import javassist.ClassPool;
import javassist.NotFoundException;
import javassist.bytecode.AccessFlag;
import javassist.bytecode.BadBytecode;
import javassist.bytecode.Bytecode;
import javassist.bytecode.ClassFile;
import javassist.bytecode.CodeAttribute;
import javassist.bytecode.CodeIterator;
import javassist.bytecode.FieldInfo;
import javassist.bytecode.MethodInfo;
import javassist.bytecode.Mnemonic;
import org.junit.Test;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.Arrays;
import java.util.LinkedList;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertTrue;
public class JavasisstUnitTest {
@Test
public void givenJavasisstAPI_whenConstructClass_thenGenerateAClassFile() throws CannotCompileException, IOException, ClassNotFoundException, IllegalAccessException, InstantiationException {
// given
String classNameWithPackage = "com.baeldung.JavassistGeneratedClass";
ClassFile cf = new ClassFile(false, classNameWithPackage, null);
cf.setInterfaces(new String[] { "java.lang.Cloneable" });
FieldInfo f = new FieldInfo(cf.getConstPool(), "id", "I");
f.setAccessFlags(AccessFlag.PUBLIC);
cf.addField(f);
// when
String className = "JavassistGeneratedClass.class";
cf.write(new DataOutputStream(new FileOutputStream(className)));
// then
ClassPool classPool = ClassPool.getDefault();
Field[] fields = classPool.makeClass(cf).toClass().getFields();
assertEquals(fields[0].getName(), "id");
String classContent = new String(Files.readAllBytes(Paths.get(className)));
assertTrue(classContent.contains("java/lang/Cloneable"));
}
@Test
public void givenJavaClass_whenLoadAtByJavassist_thenTraversWholeClass() throws NotFoundException, CannotCompileException, BadBytecode {
// given
ClassPool cp = ClassPool.getDefault();
ClassFile cf = cp.get("com.baeldung.javasisst.Point").getClassFile();
MethodInfo minfo = cf.getMethod("move");
CodeAttribute ca = minfo.getCodeAttribute();
CodeIterator ci = ca.iterator();
// when
List<String> operations = new LinkedList<>();
while (ci.hasNext()) {
int index = ci.next();
int op = ci.byteAt(index);
operations.add(Mnemonic.OPCODE[op]);
}
// then
assertEquals(operations, Arrays.asList("aload_0", "iload_1", "putfield", "aload_0", "iload_2", "putfield", "return"));
}
@Test
public void givenTableOfInstructions_whenAddNewInstruction_thenShouldConstructProperSequence() throws NotFoundException, BadBytecode, CannotCompileException, IllegalAccessException, InstantiationException {
// given
ClassFile cf = ClassPool.getDefault().get("com.baeldung.javasisst.ThreeDimensionalPoint").getClassFile();
// when
FieldInfo f = new FieldInfo(cf.getConstPool(), "id", "I");
f.setAccessFlags(AccessFlag.PUBLIC);
cf.addField(f);
ClassPool classPool = ClassPool.getDefault();
Field[] fields = classPool.makeClass(cf).toClass().getFields();
List<String> fieldsList = Stream.of(fields).map(Field::getName).collect(Collectors.toList());
assertTrue(fieldsList.contains("id"));
}
@Test
public void givenLoadedClass_whenAddConstructorToClass_shouldCreateClassWithConstructor() throws NotFoundException, CannotCompileException, BadBytecode {
// given
ClassFile cf = ClassPool.getDefault().get("com.baeldung.javasisst.Point").getClassFile();
Bytecode code = new Bytecode(cf.getConstPool());
code.addAload(0);
code.addInvokespecial("java/lang/Object", MethodInfo.nameInit, "()V");
code.addReturn(null);
// when
MethodInfo minfo = new MethodInfo(cf.getConstPool(), MethodInfo.nameInit, "()V");
minfo.setCodeAttribute(code.toCodeAttribute());
cf.addMethod(minfo);
// then
CodeIterator ci = code.toCodeAttribute().iterator();
List<String> operations = new LinkedList<>();
while (ci.hasNext()) {
int index = ci.next();
int op = ci.byteAt(index);
operations.add(Mnemonic.OPCODE[op]);
}
assertEquals(operations, Arrays.asList("aload_0", "invokespecial", "return"));
}
}
libraries/src/test/java/com/baeldung/stream/JoolMergeStreamsUnitTest.java
-34
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package com.baeldung.stream;
import org.jooq.lambda.Seq;
import org.junit.Assert;
import org.junit.Test;
import java.util.Arrays;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static junit.framework.TestCase.assertEquals;
public class JoolMergeStreamsUnitTest {
@Test
public void givenTwoStreams_whenMergingStreams_thenResultingStreamContainsElementsFromBothStreams() {
Stream<Integer> seq1 = Stream.of(1, 3, 5);
Stream<Integer> seq2 = Stream.of(2, 4, 6);
Stream<Integer> resultingSeq = Seq.ofType(seq1, Integer.class).append(seq2);
assertEquals(Arrays.asList(1, 3, 5, 2, 4, 6), resultingSeq.collect(Collectors.toList()));
}
@Test
public void givenThreeStreams_whenAppendingAndPrependingStreams_thenResultingStreamContainsElementsFromAllStreams() {
Stream<String> seq = Stream.of("foo", "bar");
Stream<String> openingBracketSeq = Stream.of("[");
Stream<String> closingBracketSeq = Stream.of("]");
Stream<String> resultingStream = Seq.ofType(seq, String.class).append(closingBracketSeq).prepend(openingBracketSeq);
Assert.assertEquals(Arrays.asList("[", "foo", "bar", "]"), resultingStream.collect(Collectors.toList()));
}
}
libraries/src/test/java/com/baeldung/stream/MergeStreamsUnitTest.java
-47
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package com.baeldung.stream;
import org.junit.Test;
import java.util.Arrays;
import java.util.function.Function;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import static org.junit.Assert.assertEquals;
public class MergeStreamsUnitTest {
@Test
public void givenTwoStreams_whenMergingStreams_thenResultingStreamContainsElementsFromBothStreams() {
Stream<Integer> stream1 = Stream.of(1, 3, 5);
Stream<Integer> stream2 = Stream.of(2, 4, 6);
Stream<Integer> resultingStream = Stream.concat(stream1, stream2);
assertEquals(Arrays.asList(1, 3, 5, 2, 4, 6), resultingStream.collect(Collectors.toList()));
}
@Test
public void givenThreeStreams_whenMergingStreams_thenResultingStreamContainsElementsFromAllStreams() {
Stream<Integer> stream1 = Stream.of(1, 3, 5);
Stream<Integer> stream2 = Stream.of(2, 4, 6);
Stream<Integer> stream3 = Stream.of(18, 15, 36);
Stream<Integer> resultingStream = Stream.concat(Stream.concat(stream1, stream2), stream3);
assertEquals(Arrays.asList(1, 3, 5, 2, 4, 6, 18, 15, 36), resultingStream.collect(Collectors.toList()));
}
@Test
public void givenFourStreams_whenMergingStreams_thenResultingStreamContainsElementsFromAllStreams() {
Stream<Integer> stream1 = Stream.of(1, 3, 5);
Stream<Integer> stream2 = Stream.of(2, 4, 6);
Stream<Integer> stream3 = Stream.of(18, 15, 36);
Stream<Integer> stream4 = Stream.of(99);
Stream<Integer> resultingStream = Stream.of(stream1, stream2, stream3, stream4).flatMap(Function.identity());
assertEquals(Arrays.asList(1, 3, 5, 2, 4, 6, 18, 15, 36, 99), resultingStream.collect(Collectors.toList()));
}
}