Java中static静态变量的初始化完全解析

public class Test { public static Test1 t = new Test1(); public static int a = 0; public static int b; public static void main(String[] arg) { System.out.println(Test.a); System.out.println(Test.b); } } class Test1 { public Test1() { Test.a++; Test.b++; } }

0 1

public class A { public static int b = B.a; public static A plus =new A("A"); public static final int finalInt = (int)(Math.random()*100); public static B p = new B("A"); public static final String finalStr = "finalStr"; public static final Integer finalInteger = new Integer(10); public static int a = 1; public static B c = null; public A(String from) { System.out.println("----------- begin A::A ----------------"); System.out.println("A::A, from="+from); System.out.println("A::A, A.b="+A.b); System.out.println("A::A, A.finalInt="+A.finalInt); System.out.println("A::A, B.a="+B.a); System.out.println("A::A, B.plus="+B.plus); System.out.println("----------- end A::A ----------------"); } public static void main(String[] arg) { System.out.println("main, A.b="+A.b); System.out.println("main, B.t="+B.t); System.out.println("main, C.a="+C.a); } } class B { public static int t = A.a; public static A plus = new A("B"); public static int a = 1; public B(String from) { System.out.println("----------- begin B::B ----------------"); System.out.println("B::B, from="+from); System.out.println("B::B, B.a="+B.a); System.out.println("B::B, A.a="+A.a); System.out.println("B::B, A.p="+A.p); System.out.println("B::B, A.plus="+A.plus); System.out.println("B::B, A.finalInt="+A.finalInt); System.out.println("B::B, A.finalInteger="+A.finalInteger); System.out.println("B::B, A.finalStr="+A.finalStr); System.out.println("----------- end B::B ----------------"); } } class C { public static final A a = new A("C"); }

----------- begin A::A ---------------- A::A, from=B A::A, A.b=0 A::A, A.finalInt=0 A::A, B.a=0 A::A, B.plus=null ----------- end A::A ---------------- ----------- begin A::A ---------------- A::A, from=A A::A, A.b=1 A::A, A.finalInt=0 A::A, B.a=1 A::A, B.plus=A@a90653 ----------- end A::A ---------------- ----------- begin B::B ---------------- B::B, from=A B::B, B.a=1 B::B, A.a=0 B::B, A.p=null B::B, A.plus=A@1fb8ee3 B::B, A.finalInt=61 B::B, A.finalInteger=null B::B, A.finalStr=finalStr ----------- end B::B ---------------- main, A.b=1 main, B.t=0 ----------- begin A::A ---------------- A::A, from=C A::A, A.b=1 A::A, A.finalInt=61 A::A, B.a=1 A::A, B.plus=A@a90653 ----------- end A::A ---------------- main, C.a=A@61de33

class Bowl { Bowl(int marker) { print("Bowl(" + marker + ")"); } void f1(int marker) { print("f1(" + marker + ")"); } } class Table { static Bowl bowl1 = new Bowl(1); Table() { print("Table()"); bowl2.f1(1); } void f2(int marker) { print("f2(" + marker + ")"); } static Bowl bowl2 = new Bowl(2); } class Cupboard { Bowl bowl3 = new Bowl(3); static Bowl bowl4 = new Bowl(4); Cupboard() { print("Cupboard()"); bowl4.f1(2); } void f3(int marker) { print("f3(" + marker + ")"); } static Bowl bowl5 = new Bowl(5); } public class StaticInitialization { public static void main(String[] args) { print("Creating new Cupboard() in main"); new Cupboard(); print("Creating new Cupboard() in main"); new Cupboard(); table.f2(1); cupboard.f3(1); } static Table table = new Table(); static Cupboard cupboard = new Cupboard(); }

Bowl(1) Bowl(2) Table() f1(1) Bowl(4) Bowl(5) Bowl(3) Cupboard() f1(2) Creating new Cupboard() in main Bowl(3) Cupboard() f1(2) Creating new Cupboard() in main Bowl(3) Cupboard() f1(2) f2(1) f3(1)

class Cup { Cup(int marker) { print("Cup(" + marker + ")"); } void f(int marker) { print("f(" + marker + ")"); } } class Cups { static Cup cup1; static Cup cup2; static { cup1 = new Cup(1); cup2 = new Cup(2); } Cups() { print("Cups()"); } } public class ExplicitStatic { public static void main(String[] args) { print("Inside main()"); Cups.cup1.f(99); // (1) } // static Cups cups1 = new Cups(); // (2) // static Cups cups2 = new Cups(); // (2) }

Inside main() Cup(1) Cup(2) f(99)

class Mug { Mug(int marker) { print("Mug(" + marker + ")"); } void f(int marker) { print("f(" + marker + ")"); } } public class Mugs { Mug mug1; Mug mug2; { mug1 = new Mug(1); mug2 = new Mug(2); print("mug1 & mug2 initialized"); } Mugs() { print("Mugs()"); } Mugs(int i) { print("Mugs(int)"); } public static void main(String[] args) { print("Inside main()"); new Mugs(); print("new Mugs() completed"); new Mugs(1); print("new Mugs(1) completed"); } }

Inside main() Mug(1) Mug(2) mug1 & mug2 initialized Mugs() new Mugs() completed Mug(1) Mug(2) mug1 & mug2 initialized Mugs(int) new Mugs(1) completed