ExecutorService executor = Executors.newFixedThreadPool(nThreads) ; +
/** + * @author Hollis + */ +public class ExecutorsDemo { + private static ExecutorService executor = Executors.newFixedThreadPool(15); + public static void main(String[] args) { + for (int i = 0; i < Integer.MAX_VALUE; i++) { + executor.execute(new SubThread()); + } + } +} + +class SubThread implements Runnable { + @Override + public void run() { + try { + Thread.sleep(10000); + } catch (InterruptedException e) { + //do nothing + } + } +} +
Exception in thread "main" java.lang.OutOfMemoryError: GC overhead limit exceeded + at java.util.concurrent.LinkedBlockingQueue.offer(LinkedBlockingQueue.java:416) + at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1371) + at com.hollis.ExecutorsDemo.main(ExecutorsDemo.java:16) +
public static ExecutorService newFixedThreadPool(int nThreads) { + return new ThreadPoolExecutor(nThreads, nThreads, + 0L, TimeUnit.MILLISECONDS, + new LinkedBlockingQueue<Runnable>()); +
private static ExecutorService executor = new ThreadPoolExecutor(10, 10, + 60L, TimeUnit.SECONDS, + new ArrayBlockingQueue(10)); +
public class ExecutorsDemo { + + private static ThreadFactory namedThreadFactory = new ThreadFactoryBuilder() + .setNameFormat("demo-pool-%d").build(); + + private static ExecutorService pool = new ThreadPoolExecutor(5, 200, + 0L, TimeUnit.MILLISECONDS, + new LinkedBlockingQueue<Runnable>(1024), namedThreadFactory, new ThreadPoolExecutor.AbortPolicy()); + + public static void main(String[] args) { + + for (int i = 0; i < Integer.MAX_VALUE; i++) { + pool.execute(new SubThread()); + } + } +} +
String s = "abcd"; -s = s.concat("ef"); -
String wechat = "Hollis"; -String introduce = "每日更新Java相关技术文章"; -String hollis = wechat + "," + introduce; -
String wechat = "Hollis"; -String introduce = "每日更新Java相关技术文章"; -String hollis = wechat.concat(",").concat(introduce); -
StringBuffer wechat = new StringBuffer("Hollis"); -String introduce = "每日更新Java相关技术文章"; -StringBuffer hollis = wechat.append(",").append(introduce); -
StringBuilder wechat = new StringBuilder("Hollis"); -String introduce = "每日更新Java相关技术文章"; -StringBuilder hollis = wechat.append(",").append(introduce); -
String wechat = "Hollis"; -String introduce = "每日更新Java相关技术文章"; -System.out.println(StringUtils.join(wechat, ",", introduce)); -
String wechat = "Hollis"; -String introduce = "\u6BCF\u65E5\u66F4\u65B0Java\u76F8\u5173\u6280\u672F\u6587\u7AE0";//每日更新Java相关技术文章 -String hollis = (new StringBuilder()).append(wechat).append(",").append(introduce).toString(); -
public String concat(String str) { - int otherLen = str.length(); - if (otherLen == 0) { - return this; + public String concat(String str) { + int otherLen = str.length(); + if (otherLen == 0) { + return this; + } + int len = value.length; + char buf[] = Arrays.copyOf(value, len + otherLen); + str.getChars(buf, len); + return new String(buf, true); } - int len = value.length; - char buf[] = Arrays.copyOf(value, len + otherLen); - str.getChars(buf, len); - return new String(buf, true); -} -
char[] value; -
int count; -
public StringBuilder append(String str) { - super.append(str); - return this; -} -
public AbstractStringBuilder append(String str) { - if (str == null) - return appendNull(); - int len = str.length(); - ensureCapacityInternal(count + len); - str.getChars(0, len, value, count); - count += len; - return this; -} -
public synchronized StringBuffer append(String str) { - toStringCache = null; - super.append(str); - return this; -} -
public static String join(final Object[] array, String separator, final int startIndex, final int endIndex) { - if (array == null) { - return null; - } - if (separator == null) { - separator = EMPTY; - } - - // endIndex - startIndex > 0: Len = NofStrings *(len(firstString) + len(separator)) - // (Assuming that all Strings are roughly equally long) - final int noOfItems = endIndex - startIndex; - if (noOfItems <= 0) { - return EMPTY; - } - - final StringBuilder buf = new StringBuilder(noOfItems * 16); - - for (int i = startIndex; i < endIndex; i++) { - if (i > startIndex) { - buf.append(separator); + public static String join(final Object[] array, String separator, final int startIndex, final int endIndex) { + if (array == null) { + return null; + } + if (separator == null) { + separator = EMPTY; + } + + // endIndex - startIndex > 0: Len = NofStrings *(len(firstString) + len(separator)) + // (Assuming that all Strings are roughly equally long) + final int noOfItems = endIndex - startIndex; + if (noOfItems <= 0) { + return EMPTY; } - if (array[i] != null) { - buf.append(array[i]); + + final StringBuilder buf = new StringBuilder(noOfItems * 16); + + for (int i = startIndex; i < endIndex; i++) { + if (i > startIndex) { + buf.append(separator); + } + if (array[i] != null) { + buf.append(array[i]); + } } + return buf.toString(); } - return buf.toString(); -} -
long t1 = System.currentTimeMillis(); -//这里是初始字符串定义 -for (int i = 0; i < 50000; i++) { - //这里是字符串拼接代码 -} -long t2 = System.currentTimeMillis(); -System.out.println("cost:" + (t2 - t1)); -
+ cost:5119 -StringBuilder cost:3 -StringBuffer cost:4 -concat cost:3623 -StringUtils.join cost:25726 -
long t1 = System.currentTimeMillis(); -String str = "hollis"; -for (int i = 0; i < 50000; i++) { - String s = String.valueOf(i); - str += s; -} -long t2 = System.currentTimeMillis(); -System.out.println("+ cost:" + (t2 - t1)); -
long t1 = System.currentTimeMillis(); -String str = "hollis"; -for(int i = 0; i < 50000; i++) -{ - String s = String.valueOf(i); - str = (new StringBuilder()).append(str).append(s).toString(); -} - -long t2 = System.currentTimeMillis(); -System.out.println((new StringBuilder()).append("+ cost:").append(t2 - t1).toString()); -
