Java Learning Lesson 25th (Multi-threaded (iv))-multithreading issues involved in a single-case design pattern

A single example design mode under multi-thread

Using the form of double judgement to solve the problem of lazy-type safety and efficiency

A hungry man-/*class single{private static final single t = new single ();p rivate single () {}public static single getinstance () {Retu RN t;}} *///Lazy class Single{private static single T = Null;private single () {}public static single getinstance () {if (t==null)// Solve the efficiency problem {synchronized (Single.class)//Resolve security Issue {if (t==null) T = new single ();}} return t;}}

so the development is still the application of a hungry man style, but in the interview to examine the lazy type, because of its high technical content

Ii. Examples of deadlocks

Deadlocks: Common is, synchronous nesting

In the interview, it will let the writing deadlock program, as long as the written out, it means that the deadlock has been understood

Class Deadlock implements Runnable{private Boolean Flag;public Deadlock (Boolean flag) {//TODO auto-generated constructor Stubthis.flag = Flag;} public void Run () {if (flag) {while (true) synchronized (lock). A_lock) {System.out.println ("If...alock"); synchronized (LOCK. B_lock) {System.out.println ("If...block");}}} else {while (true) synchronized (lock). B_lock) {System.out.println ("Else...block"); synchronized (LOCK. A_lock) {System.out.println ("Else...alock");}}}} Class Lock{public static Final Object a_lock = new Object ();p ublic static Final Object b_lock = new Object ();} Class Main{public static void Main (string[] args) {Deadlock T1 = new Deadlock (true);D eadlock t2 = new Deadlock (false); Thread J1 = new Thread (t1); Thread J2 = new Thread (t2); J1.start (); J2.start ();}}

If...alock
Else...block

It's locked, Thread-0 a lock,Thread-1 B lock .

Java Learning Lesson 25th (Multi-threaded (iv))-multithreading issues involved in a single-case design pattern