如果您有一个匿名类,例如
Predicate<String> isEmpty = new Predicate<String>() { public boolean test(String t) { return t.isEmpty(); } };
传递给引用的库isEmpty可以检查字节码以查看其作用并可能对其进行操作。有没有办法为lambda做到这一点?
isEmpty
Predicate<String> isEmpty = String::isEmpty;
例如说有这个代码和字节码
public class Main { public static void test(Predicate<String> tester) { System.out.println("tester.getClass()= " + tester.getClass()); System.out.println("tester.getClass().getClassLoader()="+ tester.getClass().getClassLoader()); } public static void main(String... args) { Predicate<String> isEmpty = String::isEmpty; test(isEmpty); } } $ javap -cp . -c -private Main.class Compiled from "Main.java" public class Main { public Main(); Code: 0: aload_0 1: invokespecial #1 // Method java/lang/Object."<init>":()V 4: return public static void test(java.util.function.Predicate<java.lang.String>); Code: 0: getstatic #2 // Field java/lang/System.out:Ljava/io/PrintStream; 3: new #3 // class java/lang/StringBuilder 6: dup 7: invokespecial #4 // Method java/lang/StringBuilder."<init>":()V 10: ldc #5 // String tester.getClass()= 12: invokevirtual #6 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 15: aload_0 16: invokevirtual #7 // Method java/lang/Object.getClass:()Ljava/lang/Class; 19: invokevirtual #8 // Method java/lang/StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder; 22: invokevirtual #9 // Method java/lang/StringBuilder.toString:()Ljava/lang/String; 25: invokevirtual #10 // Method java/io/PrintStream.println:(Ljava/lang/String;)V 28: getstatic #2 // Field java/lang/System.out:Ljava/io/PrintStream; 31: new #3 // class java/lang/StringBuilder 34: dup 35: invokespecial #4 // Method java/lang/StringBuilder."<init>":()V 38: ldc #11 // String tester.getClass().getClassLoader()= 40: invokevirtual #6 // Method java/lang/StringBuilder.append:(Ljava/lang/String;)Ljava/lang/StringBuilder; 43: aload_0 44: invokevirtual #7 // Method java/lang/Object.getClass:()Ljava/lang/Class; 47: invokevirtual #12 // Method java/lang/Class.getClassLoader:()Ljava/lang/ClassLoader; 50: invokevirtual #8 // Method java/lang/StringBuilder.append:(Ljava/lang/Object;)Ljava/lang/StringBuilder; 53: invokevirtual #9 // Method java/lang/StringBuilder.toString:()Ljava/lang/String; 56: invokevirtual #10 // Method java/io/PrintStream.println:(Ljava/lang/String;)V 59: return public static void main(java.lang.String...); Code: 0: invokedynamic #13, 0 // InvokeDynamic #0:test:()Ljava/util/function/Predicate; 5: astore_1 6: aload_1 7: invokestatic #14 // Method test:(Ljava/util/function/Predicate;)V 10: return }
有了参考tester的test我怎么觉得这方法被调用?
tester
test
如果您只想查看字节码:
javap -c -p -v classfile ^disassemble ^private methods ^verbose, including constant pool and bootstrap methods attribute
但是,如果您想尝试在运行时执行此操作,则很不走运(根据设计,我们没有像Expression Trees这样的东西),如另一个答案所示。