分析以下程序：有几个线程

package com; import java.util.Properties; /** * 分析以下程序：有几个线程。除垃圾回收线程，有几个线程 * 1个线程。因为程序只有一个栈 *main begin * m1 begin * m2 begin * m3 begin * m3 over * m2 over * m1 over * main over */ public class Test { public static void main(String[] args) throws IOException { System.out.println("main begin"); m1(); System.out.println("main over"); } private static void m1() { System.out.println("m1 begin"); m2(); System.out.println("m1 over"); } private static void m2() { System.out.println("m2 begin"); m3(); System.out.println("m2 over"); } private static void m3() { System.out.println("m3 begin"); System.out.println("m3 over"); } }