static关键字的应用场景

static关键字的应用场景

1.如初始化***池的代码，如线程池，连接池都可以使用static关键字
2.方法在类加载时，需加载，此时我们可以使用static关键字
3.一些不变的数据，在类加载时
   如:***配置文件

 
//线程池的定义

import com.google.common.util.concurrent.ThreadFactoryBuilder;
import lombok.extern.slf4j.Slf4j;
import java.util.concurrent.*;
 
@Slf4j
public class PoolUtil {
    public static final int CORE_POOL_SIZE = Runtime.getRuntime().availableProcessors() * 2;

    /**
     *初始化线程池
     * @param threadName: thread name
     * @return
     */
    public static ExecutorService initPoolExecutor(String threadName) {
        ThreadFactory guavaFactory = new ThreadFactoryBuilder().setNameFormat(threadName).build();
        ThreadPoolExecutor pool =  new ThreadPoolExecutor(CORE_POOL_SIZE,
                256,30L, TimeUnit.MILLISECONDS,
                new LinkedBlockingQueue<>(Integer.MAX_VALUE), guavaFactory);
        pool.allowsCoreThreadTimeOut();
        return pool;
    }
}

//方法及变量的初始化
class MyClass {
    public final double differentValue = Math.random(); //每次都变化
    public static double sameValue = Math.random();  //值不会变化,效率比较高
}