[JAVA-22519] Created new module libraries-stream and added 5 articles (#15403)
This commit is contained in:
panos-kakos
@@ -0,0 +1,160 @@
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package com.baeldung.asm;
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import java.io.IOException;
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import java.io.PrintWriter;
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import java.util.logging.Level;
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import java.util.logging.Logger;
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import org.objectweb.asm.ClassReader;
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import org.objectweb.asm.ClassVisitor;
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import org.objectweb.asm.ClassWriter;
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import org.objectweb.asm.FieldVisitor;
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import org.objectweb.asm.MethodVisitor;
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import static org.objectweb.asm.Opcodes.ACC_PUBLIC;
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import static org.objectweb.asm.Opcodes.ACC_STATIC;
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import static org.objectweb.asm.Opcodes.ASM4;
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import static org.objectweb.asm.Opcodes.V1_5;
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import org.objectweb.asm.Type;
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import org.objectweb.asm.util.TraceClassVisitor;
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/**
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*
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* @author baeldung
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* @param <String>
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*/
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public class CustomClassWriter {
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ClassReader reader;
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ClassWriter writer;
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AddFieldAdapter addFieldAdapter;
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AddInterfaceAdapter addInterfaceAdapter;
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PublicizeMethodAdapter pubMethAdapter;
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final static String CLASSNAME = "java.lang.Integer";
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final static String CLONEABLE = "java/lang/Cloneable";
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public CustomClassWriter() {
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try {
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reader = new ClassReader(CLASSNAME);
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writer = new ClassWriter(reader, 0);
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} catch (IOException ex) {
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Logger.getLogger(CustomClassWriter.class.getName()).log(Level.SEVERE, null, ex);
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}
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}
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public CustomClassWriter(byte[] contents) {
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reader = new ClassReader(contents);
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writer = new ClassWriter(reader, 0);
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}
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public static void main(String[] args) {
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CustomClassWriter ccw = new CustomClassWriter();
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ccw.publicizeMethod();
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}
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public byte[] addField() {
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addFieldAdapter = new AddFieldAdapter("aNewBooleanField", org.objectweb.asm.Opcodes.ACC_PUBLIC, writer);
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reader.accept(addFieldAdapter, 0);
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return writer.toByteArray();
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}
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public byte[] publicizeMethod() {
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pubMethAdapter = new PublicizeMethodAdapter(writer);
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reader.accept(pubMethAdapter, 0);
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return writer.toByteArray();
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}
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public byte[] addInterface() {
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addInterfaceAdapter = new AddInterfaceAdapter(writer);
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reader.accept(addInterfaceAdapter, 0);
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return writer.toByteArray();
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}
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public class AddInterfaceAdapter extends ClassVisitor {
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public AddInterfaceAdapter(ClassVisitor cv) {
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super(ASM4, cv);
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}
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@Override
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public void visit(int version, int access, String name,
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String signature, String superName, String[] interfaces) {
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String[] holding = new String[interfaces.length + 1];
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holding[holding.length - 1] = CLONEABLE;
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System.arraycopy(interfaces, 0, holding, 0, interfaces.length);
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cv.visit(V1_5, access, name, signature, superName, holding);
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}
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}
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public class PublicizeMethodAdapter extends ClassVisitor {
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final Logger logger = Logger.getLogger("PublicizeMethodAdapter");
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TraceClassVisitor tracer;
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PrintWriter pw = new PrintWriter(System.out);
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public PublicizeMethodAdapter(ClassVisitor cv) {
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super(ASM4, cv);
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this.cv = cv;
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tracer = new TraceClassVisitor(cv, pw);
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}
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@Override
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public MethodVisitor visitMethod(int access,
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String name,
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String desc,
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String signature,
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String[] exceptions) {
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if (name.equals("toUnsignedString0")) {
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logger.info("Visiting unsigned method");
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return tracer.visitMethod(ACC_PUBLIC + ACC_STATIC, name, desc, signature, exceptions);
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}
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return tracer.visitMethod(access, name, desc, signature, exceptions);
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}
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public void visitEnd() {
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tracer.visitEnd();
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System.out.println(tracer.p.getText());
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}
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}
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public class AddFieldAdapter extends ClassVisitor {
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String fieldName;
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int access;
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boolean isFieldPresent;
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public AddFieldAdapter(String fieldName, int access, ClassVisitor cv) {
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super(ASM4, cv);
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this.cv = cv;
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this.access = access;
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this.fieldName = fieldName;
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}
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@Override
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public FieldVisitor visitField(int access, String name, String desc,
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String signature, Object value) {
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if (name.equals(fieldName)) {
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isFieldPresent = true;
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}
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return cv.visitField(access, name, desc, signature, value);
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}
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@Override
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public void visitEnd() {
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if (!isFieldPresent) {
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FieldVisitor fv = cv.visitField(access, fieldName, Type.BOOLEAN_TYPE.toString(), null, null);
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if (fv != null) {
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fv.visitEnd();
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}
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}
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cv.visitEnd();
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}
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}
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}
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@@ -0,0 +1,32 @@
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package com.baeldung.asm.instrumentation;
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import com.baeldung.asm.CustomClassWriter;
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import java.lang.instrument.ClassFileTransformer;
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import java.lang.instrument.IllegalClassFormatException;
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import java.lang.instrument.Instrumentation;
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import java.security.ProtectionDomain;
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/**
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*
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* @author baeldung
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*/
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public class Premain {
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public static void premain(String agentArgs, Instrumentation inst) {
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inst.addTransformer(new ClassFileTransformer() {
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@Override
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public byte[] transform(ClassLoader l, String name, Class c,
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ProtectionDomain d, byte[] b)
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throws IllegalClassFormatException {
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if (name.equals("java/lang/Integer")) {
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CustomClassWriter cr = new CustomClassWriter(b);
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return cr.addField();
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}
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return b;
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}
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});
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}
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}
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@@ -0,0 +1,21 @@
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package com.baeldung.bytebuddy;
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import net.bytebuddy.implementation.bind.annotation.BindingPriority;
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public class Bar {
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@BindingPriority(3)
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public static String sayHelloBar() {
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return "Holla in Bar!";
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}
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@BindingPriority(2)
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public static String sayBar() {
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return "bar";
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}
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public String bar() {
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return Bar.class.getSimpleName() + " - Bar";
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}
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}
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@@ -0,0 +1,9 @@
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package com.baeldung.bytebuddy;
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public class Foo {
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public String sayHelloFoo() {
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return "Hello in Foo!";
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}
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}
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@@ -0,0 +1,16 @@
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package com.baeldung.javasisst;
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public class Point {
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public int x = 0;
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public int y = 0;
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public Point(int x, int y) {
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this.x = x;
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this.y = y;
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}
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public void move(int x, int y) {
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this.x = x;
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this.y = y;
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}
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}
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@@ -0,0 +1,18 @@
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package com.baeldung.javasisst;
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public class ThreeDimensionalPoint {
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public int x = 0;
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public int y = 0;
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public int z = 0;
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public ThreeDimensionalPoint(int x, int y, int z) {
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this.x = x;
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this.y = y;
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this.z = z;
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}
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public void move(int x, int y) {
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this.x = x;
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this.y = y;
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}
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}
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@@ -0,0 +1,13 @@
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<?xml version="1.0" encoding="UTF-8"?>
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<configuration>
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<appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
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<encoder>
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<pattern>%d{HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n
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</pattern>
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</encoder>
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</appender>
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<root level="INFO">
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<appender-ref ref="STDOUT" />
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</root>
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</configuration>
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@@ -0,0 +1,63 @@
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package com.baeldung.bytebuddy;
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import static net.bytebuddy.matcher.ElementMatchers.isDeclaredBy;
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import static net.bytebuddy.matcher.ElementMatchers.named;
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import static net.bytebuddy.matcher.ElementMatchers.returns;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertNotNull;
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import java.lang.reflect.Method;
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import java.lang.reflect.Modifier;
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import org.junit.Test;
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import net.bytebuddy.ByteBuddy;
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import net.bytebuddy.agent.ByteBuddyAgent;
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import net.bytebuddy.dynamic.DynamicType;
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import net.bytebuddy.dynamic.loading.ClassLoadingStrategy;
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import net.bytebuddy.dynamic.loading.ClassReloadingStrategy;
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import net.bytebuddy.implementation.FixedValue;
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import net.bytebuddy.implementation.MethodDelegation;
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import net.bytebuddy.matcher.ElementMatchers;
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public class ByteBuddyUnitTest {
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@Test
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public void givenObject_whenToString_thenReturnHelloWorldString() throws InstantiationException, IllegalAccessException {
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DynamicType.Unloaded unloadedType = new ByteBuddy().subclass(Object.class).method(ElementMatchers.isToString()).intercept(FixedValue.value("Hello World ByteBuddy!")).make();
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Class<?> dynamicType = unloadedType.load(getClass().getClassLoader()).getLoaded();
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assertEquals(dynamicType.newInstance().toString(), "Hello World ByteBuddy!");
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}
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@Test
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public void givenFoo_whenRedefined_thenReturnFooRedefined() throws Exception {
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ByteBuddyAgent.install();
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new ByteBuddy().redefine(Foo.class).method(named("sayHelloFoo")).intercept(FixedValue.value("Hello Foo Redefined")).make().load(Foo.class.getClassLoader(), ClassReloadingStrategy.fromInstalledAgent());
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Foo f = new Foo();
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assertEquals(f.sayHelloFoo(), "Hello Foo Redefined");
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}
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@Test
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public void givenSayHelloFoo_whenMethodDelegation_thenSayHelloBar() throws IllegalAccessException, InstantiationException {
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String r = new ByteBuddy().subclass(Foo.class).method(named("sayHelloFoo").and(isDeclaredBy(Foo.class).and(returns(String.class)))).intercept(MethodDelegation.to(Bar.class)).make().load(getClass().getClassLoader()).getLoaded().newInstance()
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.sayHelloFoo();
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assertEquals(r, Bar.sayHelloBar());
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}
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@Test
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public void givenMethodName_whenDefineMethod_thenCreateMethod() throws Exception {
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Class<?> type = new ByteBuddy().subclass(Object.class).name("MyClassName").defineMethod("custom", String.class, Modifier.PUBLIC).intercept(MethodDelegation.to(Bar.class)).defineField("x", String.class, Modifier.PUBLIC).make()
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.load(getClass().getClassLoader(), ClassLoadingStrategy.Default.WRAPPER).getLoaded();
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Method m = type.getDeclaredMethod("custom", null);
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assertEquals(m.invoke(type.newInstance()), Bar.sayHelloBar());
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assertNotNull(type.getDeclaredField("x"));
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}
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}
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@@ -0,0 +1,122 @@
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package com.baeldung.javassist;
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import javassist.CannotCompileException;
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import javassist.ClassPool;
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import javassist.NotFoundException;
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import javassist.bytecode.AccessFlag;
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import javassist.bytecode.BadBytecode;
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import javassist.bytecode.Bytecode;
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import javassist.bytecode.ClassFile;
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import javassist.bytecode.CodeAttribute;
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import javassist.bytecode.CodeIterator;
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import javassist.bytecode.FieldInfo;
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import javassist.bytecode.MethodInfo;
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import javassist.bytecode.Mnemonic;
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import org.junit.Test;
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import java.io.DataOutputStream;
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import java.io.FileOutputStream;
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import java.io.IOException;
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import java.lang.reflect.Field;
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import java.nio.file.Files;
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import java.nio.file.Paths;
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import java.util.Arrays;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertTrue;
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public class JavasisstUnitTest {
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@Test
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public void givenJavasisstAPI_whenConstructClass_thenGenerateAClassFile() throws CannotCompileException, IOException, ClassNotFoundException, IllegalAccessException, InstantiationException {
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// given
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String classNameWithPackage = "com.baeldung.JavassistGeneratedClass";
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ClassFile cf = new ClassFile(false, classNameWithPackage, null);
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cf.setInterfaces(new String[] { "java.lang.Cloneable" });
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FieldInfo f = new FieldInfo(cf.getConstPool(), "id", "I");
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f.setAccessFlags(AccessFlag.PUBLIC);
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cf.addField(f);
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// when
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String className = "JavassistGeneratedClass.class";
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cf.write(new DataOutputStream(new FileOutputStream(className)));
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// then
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ClassPool classPool = ClassPool.getDefault();
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Field[] fields = classPool.makeClass(cf).toClass().getFields();
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assertEquals(fields[0].getName(), "id");
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String classContent = new String(Files.readAllBytes(Paths.get(className)));
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assertTrue(classContent.contains("java/lang/Cloneable"));
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}
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@Test
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public void givenJavaClass_whenLoadAtByJavassist_thenTraversWholeClass() throws NotFoundException, CannotCompileException, BadBytecode {
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// given
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ClassPool cp = ClassPool.getDefault();
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ClassFile cf = cp.get("com.baeldung.javasisst.Point").getClassFile();
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MethodInfo minfo = cf.getMethod("move");
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CodeAttribute ca = minfo.getCodeAttribute();
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CodeIterator ci = ca.iterator();
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// when
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List<String> operations = new LinkedList<>();
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while (ci.hasNext()) {
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int index = ci.next();
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int op = ci.byteAt(index);
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operations.add(Mnemonic.OPCODE[op]);
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}
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// then
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assertEquals(operations, Arrays.asList("aload_0", "iload_1", "putfield", "aload_0", "iload_2", "putfield", "return"));
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}
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@Test
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public void givenTableOfInstructions_whenAddNewInstruction_thenShouldConstructProperSequence() throws NotFoundException, BadBytecode, CannotCompileException, IllegalAccessException, InstantiationException {
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// given
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ClassFile cf = ClassPool.getDefault().get("com.baeldung.javasisst.ThreeDimensionalPoint").getClassFile();
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// when
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FieldInfo f = new FieldInfo(cf.getConstPool(), "id", "I");
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f.setAccessFlags(AccessFlag.PUBLIC);
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cf.addField(f);
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ClassPool classPool = ClassPool.getDefault();
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Field[] fields = classPool.makeClass(cf).toClass().getFields();
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List<String> fieldsList = Stream.of(fields).map(Field::getName).collect(Collectors.toList());
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assertTrue(fieldsList.contains("id"));
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}
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@Test
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public void givenLoadedClass_whenAddConstructorToClass_shouldCreateClassWithConstructor() throws NotFoundException, CannotCompileException, BadBytecode {
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// given
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ClassFile cf = ClassPool.getDefault().get("com.baeldung.javasisst.Point").getClassFile();
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Bytecode code = new Bytecode(cf.getConstPool());
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code.addAload(0);
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code.addInvokespecial("java/lang/Object", MethodInfo.nameInit, "()V");
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code.addReturn(null);
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// when
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MethodInfo minfo = new MethodInfo(cf.getConstPool(), MethodInfo.nameInit, "()V");
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minfo.setCodeAttribute(code.toCodeAttribute());
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cf.addMethod(minfo);
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// then
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CodeIterator ci = code.toCodeAttribute().iterator();
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List<String> operations = new LinkedList<>();
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while (ci.hasNext()) {
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int index = ci.next();
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int op = ci.byteAt(index);
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operations.add(Mnemonic.OPCODE[op]);
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}
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assertEquals(operations, Arrays.asList("aload_0", "invokespecial", "return"));
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}
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}
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