一、源碼
1、屬性
private final ThreadGroup parent; 父線程組對象 String name; 線程組名稱 int maxPriority; 最高優先級 boolean destroyed; 是否已銷毀 boolean daemon; 是否是守護線程 boolean vmAllowSuspension; 虛擬機自動掛起 int nUnstartedThreads = 0; 未啟動線程數 int nthreads; 線程總數 Thread threads[]; 線程數組 int ngroups; 線程組數量 ThreadGroup groups[]; 線程組數組
2、構造方法
private ThreadGroup() { // called from C code
this.name = "system";
this.maxPriority = Thread.MAX_PRIORITY;
this.parent = null;
}
public ThreadGroup(String name) {
this(Thread.currentThread().getThreadGroup(), name);
}
public ThreadGroup(ThreadGroup parent, String name) {
this(checkParentAccess(parent), parent, name);
}
private ThreadGroup(Void unused, ThreadGroup parent, String name) {
this.name = name;
this.maxPriority = parent.maxPriority;
this.daemon = parent.daemon;
this.vmAllowSuspension = parent.vmAllowSuspension;
this.parent = parent;
parent.add(this);
}
3、一般方法
private static Void checkParentAccess(ThreadGroup parent) {
parent.checkAccess();
return null;
}
確認權限
public final String getName() {
return name;
}
獲得線程組名稱
public final ThreadGroup getParent() {
if (parent != null)
parent.checkAccess();
return parent;
}
獲得父線程組
public final int getMaxPriority() {
return maxPriority;
}
獲得最高優先級
public final boolean isDaemon() {
return daemon;
}
是否守護線程
public synchronized boolean isDestroyed() {
return destroyed;
}
是否已銷毀
public final void setDaemon(boolean daemon) {
checkAccess();
this.daemon = daemon;
}
設置守護線程
public final void checkAccess() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkAccess(this);
}
}
確認權限
public final void setMaxPriority(int pri) {
int ngroupsSnapshot;
ThreadGroup[] groupsSnapshot;
synchronized (this) {
checkAccess();
if (pri < Thread.MIN_PRIORITY || pri > Thread.MAX_PRIORITY) {
return;
}
//如果有父分組，取優先級小的值
maxPriority = (parent != null) ? Math.min(pri, parent.maxPriority) : pri;
ngroupsSnapshot = ngroups;
if (groups != null) {
groupsSnapshot = Arrays.copyOf(groups, ngroupsSnapshot);
} else {
groupsSnapshot = null;
}
}
//設置當前線程組中每組的優先級
for (int i = 0 ; i < ngroupsSnapshot ; i++) {
groupsSnapshot[i].setMaxPriority(pri);
}
}
設置最大優先級
public final boolean parentOf(ThreadGroup g) {
for (; g != null ; g = g.parent) {
if (g == this) {
return true;
}
}
return false;
}
是否是其祖先線程組
public final void checkAccess() {
SecurityManager security = System.getSecurityManager();
if (security != null) {
security.checkAccess(this);
}
}
權限相關
public int activeCount() {
int result;
int ngroupsSnapshot;
ThreadGroup[] groupsSnapshot;
synchronized (this) {
if (destroyed) {
return 0;
}
result = nthreads;
ngroupsSnapshot = ngroups;
if (groups != null) {
groupsSnapshot = Arrays.copyOf(groups, ngroupsSnapshot);
} else {
groupsSnapshot = null;
}
}
for (int i = 0 ; i < ngroupsSnapshot ; i++) {
result += groupsSnapshot[i].activeCount();
}
return result;
}
獲得當前線程組和子孫線程組的線程總數
public int enumerate(Thread list[]) {
checkAccess();
return enumerate(list, 0, true);
}
public int enumerate(Thread list[], boolean recurse) {
checkAccess();
return enumerate(list, 0, recurse);
}
private int enumerate(Thread list[], int n, boolean recurse) {
int ngroupsSnapshot = 0;
ThreadGroup[] groupsSnapshot = null;
synchronized (this) {
if (destroyed) {
return 0;
}
int nt = nthreads;
if (nt > list.length - n) {
nt = list.length - n;
}
for (int i = 0; i < nt; i++) {
if (threads[i].isAlive()) {
list[n++] = threads[i];
}
}
if (recurse) {
ngroupsSnapshot = ngroups;
if (groups != null) {
groupsSnapshot = Arrays.copyOf(groups, ngroupsSnapshot);
} else {
groupsSnapshot = null;
}
}
}
if (recurse) {
for (int i = 0 ; i < ngroupsSnapshot ; i++) {
n = groupsSnapshot[i].enumerate(list, n, true);
}
}
return n;
}
將線程組和子線程組的線程復制到數組中
public int activeGroupCount() {
int ngroupsSnapshot;
ThreadGroup[] groupsSnapshot;
synchronized (this) {
if (destroyed) {
return 0;
}
ngroupsSnapshot = ngroups;
if (groups != null) {
groupsSnapshot = Arrays.copyOf(groups, ngroupsSnapshot);
} else {
groupsSnapshot = null;
}
}
int n = ngroupsSnapshot;
for (int i = 0 ; i < ngroupsSnapshot ; i++) {
n += groupsSnapshot[i].activeGroupCount();
}
return n;
}
獲得線程組和子線程組的數量
public int enumerate(ThreadGroup list[]) {
checkAccess();
return enumerate(list, 0, true);
}
public int enumerate(ThreadGroup list[], boolean recurse) {
checkAccess();
return enumerate(list, 0, recurse);
}
private int enumerate(ThreadGroup list[], int n, boolean recurse) {
int ngroupsSnapshot = 0;
ThreadGroup[] groupsSnapshot = null;
synchronized (this) {
if (destroyed) {
return 0;
}
int ng = ngroups;
if (ng > list.length - n) {
ng = list.length - n;
}
if (ng > 0) {
System.arraycopy(groups, 0, list, n, ng);
n += ng;
}
if (recurse) {
ngroupsSnapshot = ngroups;
if (groups != null) {
groupsSnapshot = Arrays.copyOf(groups, ngroupsSnapshot);
} else {
groupsSnapshot = null;
}
}
}
if (recurse) {
for (int i = 0 ; i < ngroupsSnapshot ; i++) {
n = groupsSnapshot[i].enumerate(list, n, true);
}
}
return n;
}
將線程組和子線程組復制到數組中
public final void interrupt() {
int ngroupsSnapshot;
ThreadGroup[] groupsSnapshot;
synchronized (this) {
checkAccess();
for (int i = 0 ; i < nthreads ; i++) {
threads[i].interrupt();
}
ngroupsSnapshot = ngroups;
if (groups != null) {
groupsSnapshot = Arrays.copyOf(groups, ngroupsSnapshot);
} else {
groupsSnapshot = null;
}
}
for (int i = 0 ; i < ngroupsSnapshot ; i++) {
groupsSnapshot[i].interrupt();
}
}
暫停所有線程
public final void destroy() {
int ngroupsSnapshot;
ThreadGroup[] groupsSnapshot;
synchronized (this) {
checkAccess();
if (destroyed || (nthreads > 0)) {
throw new IllegalThreadStateException();
}
ngroupsSnapshot = ngroups;
if (groups != null) {
groupsSnapshot = Arrays.copyOf(groups, ngroupsSnapshot);
} else {
groupsSnapshot = null;
}
if (parent != null) {
destroyed = true;
ngroups = 0;
groups = null;
nthreads = 0;
threads = null;
}
}
for (int i = 0 ; i < ngroupsSnapshot ; i += 1) {
groupsSnapshot[i].destroy();
}
if (parent != null) {
parent.remove(this);
}
}
銷毀所有線程組和子組，包含的線程必須為空
private final void add(ThreadGroup g){
synchronized (this) {
if (destroyed) {
throw new IllegalThreadStateException();
}
if (groups == null) {
groups = new ThreadGroup[4];
} else if (ngroups == groups.length) {
groups = Arrays.copyOf(groups, ngroups * 2);
}
groups[ngroups] = g;
ngroups++;
}
}
新增線程組，數組初始化是4個，之后每次滿了之后翻倍
private void remove(ThreadGroup g) {
synchronized (this) {
if (destroyed) {
return;
}
for (int i = 0 ; i < ngroups ; i++) {
if (groups[i] == g) {
ngroups -= 1;
System.arraycopy(groups, i + 1, groups, i, ngroups - i);
groups[ngroups] = null;
break;
}
}
if (nthreads == 0) {
notifyAll();
}
if (daemon && (nthreads == 0) &&
(nUnstartedThreads == 0) && (ngroups == 0))
{
destroy();
}
}
}
移除線程組
void addUnstarted() {
synchronized(this) {
if (destroyed) {
throw new IllegalThreadStateException();
}
nUnstartedThreads++;
}
}
增加線程組數量
void add(Thread t) {
synchronized (this) {
if (destroyed) {
throw new IllegalThreadStateException();
}
if (threads == null) {
threads = new Thread[4];
} else if (nthreads == threads.length) {
threads = Arrays.copyOf(threads, nthreads * 2);
}
threads[nthreads] = t;
nthreads++;
nUnstartedThreads--;
}
}
增加線程
void threadStartFailed(Thread t) {
synchronized(this) {
remove(t);
nUnstartedThreads++;
}
}
線程啟動失敗
void threadTerminated(Thread t) {
synchronized (this) {
remove(t);
if (nthreads == 0) {
notifyAll();
}
if (daemon && (nthreads == 0) &&
(nUnstartedThreads == 0) && (ngroups == 0))
{
destroy();
}
}
}
終止線程
private void remove(Thread t) {
synchronized (this) {
if (destroyed) {
return;
}
for (int i = 0 ; i < nthreads ; i++) {
if (threads[i] == t) {
System.arraycopy(threads, i + 1, threads, i, --nthreads - i);
// Zap dangling reference to the dead thread so that
// the garbage collector will collect it.
threads[nthreads] = null;
break;
}
}
}
}
移除線程
public void list() {
list(System.out, 0);
}
void list(PrintStream out, int indent) {
int ngroupsSnapshot;
ThreadGroup[] groupsSnapshot;
synchronized (this) {
for (int j = 0 ; j < indent ; j++) {
out.print(" ");
}
out.println(this);
indent += 4;
for (int i = 0 ; i < nthreads ; i++) {
for (int j = 0 ; j < indent ; j++) {
out.print(" ");
}
out.println(threads[i]);
}
ngroupsSnapshot = ngroups;
if (groups != null) {
groupsSnapshot = Arrays.copyOf(groups, ngroupsSnapshot);
} else {
groupsSnapshot = null;
}
}
for (int i = 0 ; i < ngroupsSnapshot ; i++) {
groupsSnapshot[i].list(out, indent);
}
}
打印線程組列表信息
public void uncaughtException(Thread t, Throwable e) {
if (parent != null) {
parent.uncaughtException(t, e);
} else {
Thread.UncaughtExceptionHandler ueh =
Thread.getDefaultUncaughtExceptionHandler();
if (ueh != null) {
ueh.uncaughtException(t, e);
} else if (!(e instanceof ThreadDeath)) {
System.err.print("Exception in thread \"" + t.getName() + "\" ");
e.printStackTrace(System.err);
}
}
}
實現了未捕獲異常方法，優先調用當前線程的異常handler，沒有的話調用全局的默認異常handler，如果還沒有就執行e.printStackTrace
public String toString() {
return getClass().getName() + "[name=" + getName() + ",maxpri=" + maxPriority + "]";
}
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