java8-stack-stackwalking

manual

• theory: https://github.com/mtumilowicz/java-stack
• StackTraceElement class represents a stack frame
  • useful methods:
    • int getLineNumber()
    • String getClassName()
    • String getMethodName()
• to get all frames of the current thread's stack
  • first element of the array is the top frame in the stack (last method invocation)
  • StackTraceElement[] frames = new Throwable().getStackTrace();
  • StackTraceElement[] frames = Thread.currentThread().getStackTrace();
• drawbacks:
  • getStrackTrace() returns entire stack - we may need only top 5 elements for example
  • no easy way to filter
  • StackTraceElement contains method names and class names, but we often need class references

project description

1. for test purposes

   class StackWalking {
   void m1() {
   m2();
   }
   private void m2() {
   m3();
   }
   private void m3() {
   System.out.println("---");
   System.out.println("stack from m3():");
   Arrays.stream(new Throwable().getStackTrace()) // getStackTrace on Throwable
   .forEach(System.out::println);
   System.out.println("---");
   m4();
   }
   private void m4() {
   System.out.println("---");
   System.out.println("stack from m4():");
   Arrays.stream(Thread.currentThread().getStackTrace()) // getStackTrace on Thread
   .forEach(System.out::println);
   System.out.println("---");
   }
   }
   

2. simulation

   @Test
   public void simulation() {
   new StackWalking().m1();
   }
   

   produces:

   ---
   stack from m3():
   StackWalking.m3(StackWalking.java:18)
   StackWalking.m2(StackWalking.java:12)
   StackWalking.m1(StackWalking.java:8)
   StackWalkingTest.simulation(StackWalkingTest.java:10)
   ... // other
   ---
   ---
   stack from m4():
   java.base/java.lang.Thread.getStackTrace(Thread.java:1606)
   StackWalking.m4(StackWalking.java:28)
   StackWalking.m3(StackWalking.java:22)
   StackWalking.m2(StackWalking.java:12)
   StackWalking.m1(StackWalking.java:8)
   StackWalkingTest.simulation(StackWalkingTest.java:10)
   .. // other
   ---