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？
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？
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。
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我来说两句