java certification levels

Four Ways of sychronized keywords Sychronized method () {} Sychronized (objectreference) {/*block*/} Static Synchronized Method () {} Sychronized (Classname.class) where 1 and 2 represent the current object of the lock, that is, an object is a lock, and 3 and 4 represent the lock class, that is, the lock of this class. Note that sychronized method () is not a lock function, but rather a lock object, namely: If two of the methods in this class are sychronized, then as long as two threads sh

1. PrefaceHotspot has adopted a accessibility analysis algorithm to determine whether an object can be used by a GC, whether it is a reference or an accessibility analysis algorithm to determine whether an object exists or not. If the value stored in the data of type reference represents the starting address of another piece of memory, it is said that this memory represents a reference. To enrich the description of the relationship between objects and objects, in order to implement the system ca

Package-privateThis describes the access level of the Java class in the official guidance: At the top level-public, or package-private (no explicit modifier). At the member Level-public, private, protected, or package-private (no explicit modifier). Do not know what package-private is, so continue to look down, see such a passage: A class may being declared with the modifier public, in which case, which is visible to all cla

Four Ways of sychronized keywords Sychronized method () {} Sychronized (objectreference) {/*block*/} Static Synchronized Method () {} Sychronized (Classname.class) where 1 and 2 represent the current object of the lock, that is, an object is a lock, and 3 and 4 represent the lock class, that is, the lock of this class. Note that sychronized method () is not a lock function, but rather a lock object, namely: If two of the methods in this class are sychronized, then as long as two threads sh

in the tireless practice, the time can let himself to another level (2) Think too much, do too little: want to see everything, nothing to look carefully, heard, they do not use How to get the law: (1) Deliberate practice: Split to the most fine grain size, for each of the intentional contact, so that they always stay in the not very comfortable learning state (2) The best sense of humor: learning is very dull, time tension will make people grumpy, mentality imbalance, have to have the a

, a hunger-like phenomenon will occur and the thread will stop.No Wait (wait-free)No lock requires only one thread to complete the operation within a finite step, while no waiting is further extended on a lock-free basis. It requires all threads to be completed in a limited number of steps, so that they do not cause hunger problems. If you limit the upper limit of this step, you can further decompose the no wait to have no waiting and the number of threads regardless of the few, the difference b