//this引用逃逸
// 1.构造器还未完成前,将自身this引用向外抛,使其他线程访问这个引用,进而访问到其未初始化的变量,造成问题
// 2.内部类访问外部类未初始化的成员变量
//3.多态继承中,父类访问子类未初始化的成员变量
public class TestThisEscape {
final int a;
int b = 3;
static TestThisEscape obj;
public TestThisEscape(){
a= 3;
b= 5;
//obj = new TestThisEscape(); //在构造器中很明显抛出引用会造成this引用逃逸
} public static void main(String[] args) {
Thread threadA = new Thread(new Runnable() {
@Override
public void run() {
System.out.println("---------------");
obj = new TestThisEscape();
System.out.println("============");
}
},"threadA"); Thread threadB = new Thread(new Runnable() {
@Override
public void run() {
TestThisEscape obj1 = obj;//obj未初始化完成,this引用被使用造成空指针一场
// try {
System.out.println(obj1.a);
//} catch (Exception e) {
System.out.println(Thread.currentThread().getName()+" a变量未初始化");
//}
try {
System.out.println(obj1.b);
} catch (Exception e) {
System.out.println(Thread.currentThread().getName()+" b变量未初始化");
}
}
},"threadB");
threadA.start();
threadB.start();
}}
/**
* this逸出条件:1.构造函数中创建内部类。2.构造函数中将这个内部类的引用发布了出去
*/
public class TestInnerClassThisEscape {
final int a;
int b = 3;
String c;
static TestInnerClassThisEscape obj;
public TestInnerClassThisEscape(){
new Thread(new Runnable() {
@Override
public void run() {
System.out.println(TestInnerClassThisEscape.this.a);
System.out.println(TestInnerClassThisEscape.this.b);
System.out.println(TestInnerClassThisEscape.this.c);
}
}).start();
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
a= 3;
b= 5; } public static void main(String[] args) {
new TestInnerClassThisEscape();
}}
public class TestThisPC {
public static void main(String[] args) {
new Child();
}
}
class Parent{
Parent(){
print();
}
void print(){
System.out.println("----------");
}
}class Child extends Parent{
int a = 5;
void print(){
System.out.println("-----------"+ a);
}
Child(){
super();
print();
}
}
解决方案:
1.初始化在调用之前