java字符串与数组比较_字符串与字符数组有区别吗

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#include “precompiled.hpp”

#include “classfile/javaClasses.hpp”

#include “classfile/systemDictionary.hpp”

#include “classfile/vmSymbols.hpp”

#include “gc/shared/collectedHeap.inline.hpp”

#include “jvmtifiles/jvmti.h”

#include “memory/metaspaceClosure.hpp”

#include “memory/resourceArea.hpp”

#include “memory/universe.hpp”

#include “oops/arrayKlass.hpp”

#include “oops/arrayOop.hpp”

#include “oops/instanceKlass.hpp”

#include “oops/objArrayOop.hpp”

#include “oops/oop.inline.hpp”

#include “runtime/handles.inline.hpp”

int ArrayKlass::static_size(int header_size) {

// size of an array klass object

assert(header_size <= InstanceKlass::header_size(), “bad header size”);

// If this assert fails, see comments in base_create_array_klass.

header_size = InstanceKlass::header_size();

int vtable_len = Universe::base_vtable_size();

int size = header_size + vtable_len;

return align_metadata_size(size);

}

Klass* ArrayKlass::java_super() const {

if (super() == NULL) return NULL; // bootstrap case

// Array klasses have primary supertypes which are not reported to Java.

// Example super chain: String[][] -> Object[][] -> Object[] -> Object

return SystemDictionary::Object_klass();

}

oop ArrayKlass::multi_allocate(int rank, jint* sizes, TRAPS) {

ShouldNotReachHere();

return NULL;

}

// find field according to JVM spec 5.4.3.2, returns the klass in which the field is defined

Klass* ArrayKlass::find_field(Symbol* name, Symbol* sig, fieldDescriptor* fd) const {

// There are no fields in an array klass but look to the super class (Object)

assert(super(), “super klass must be present”);

return super()->find_field(name, sig, fd);

}

Method* ArrayKlass::uncached_lookup_method(const Symbol* name,

const Symbol* signature,

OverpassLookupMode overpass_mode,

PrivateLookupMode private_mode) const {

// There are no methods in an array klass but the super class (Object) has some

assert(super(), “super klass must be present”);

// Always ignore overpass methods in superclasses, although technically the

// super klass of an array, (j.l.Object) should not have

// any overpass methods present.

return super()->uncached_lookup_method(name, signature, Klass::skip_overpass, private_mode);

}

ArrayKlass::ArrayKlass(Symbol* name, KlassID id) :

Klass(id),

_dimension(1),

_higher_dimension(NULL),

_lower_dimension(NULL) {

// Arrays don’t add any new methods, so their vtable is the same size as

// the vtable of klass Object.

set_vtable_length(Universe::base_vtable_size());

set_name(name);

set_super(Universe::is_bootstrapping() ? (Klass*)NULL : SystemDictionary::Object_klass());

set_layout_helper(Klass::_lh_neutral_value);

set_is_cloneable(); // All arrays are considered to be cloneable (See JLS 20.1.5)

JFR_ONLY(INIT_ID(this);)

}

// Initialization of vtables and mirror object is done separatly from base_create_array_klass,

// since a GC can happen. At this point all instance variables of the ArrayKlass must be setup.

void ArrayKlass::complete_create_array_klass(ArrayKlass* k, Klass* super_klass, ModuleEntry* module_entry, TRAPS) {

ResourceMark rm(THREAD);

k->initialize_supers(super_klass, NULL, CHECK);

k->vtable().initialize_vtable(false, CHECK);

// During bootstrapping, before java.base is defined, the module_entry may not be present yet.

// These classes will be put on a fixup list and their module fields will be patched once

// java.base is defined.

assert((module_entry != NULL) || ((module_entry == NULL) && !ModuleEntryTable::javabase_defined()),

“module entry not available post ” JAVA_BASE_NAME ” definition”);

oop module = (module_entry != NULL) ? module_entry->module() : (oop)NULL;

java_lang_Class::create_mirror(k, Handle(THREAD, k->class_loader()), Handle(THREAD, module), Handle(), CHECK);

}

GrowableArray* ArrayKlass::compute_secondary_supers(int num_extra_slots,

Array* transitive_interfaces) {

// interfaces = { cloneable_klass, serializable_klass };

assert(num_extra_slots == 0, “sanity of primitive array type”);

assert(transitive_interfaces == NULL, “sanity”);

// Must share this for correct bootstrapping!

set_secondary_supers(Universe::the_array_interfaces_array());

return NULL;

}

bool ArrayKlass::compute_is_subtype_of(Klass* k) {

// An array is a subtype of Serializable, Clonable, and Object

return k == SystemDictionary::Object_klass()

|| k == SystemDictionary::Cloneable_klass()

|| k == SystemDictionary::Serializable_klass();

}

objArrayOop ArrayKlass::allocate_arrayArray(int n, int length, TRAPS) {

if (length < 0) {

THROW_MSG_0(vmSymbols::java_lang_NegativeArraySizeException(), err_msg(“%d”, length));

}

if (length > arrayOopDesc::max_array_length(T_ARRAY)) {

report_java_out_of_memory(“Requested array size exceeds VM limit”);

JvmtiExport::post_array_size_exhausted();

THROW_OOP_0(Universe::out_of_memory_error_array_size());

}

int size = objArrayOopDesc::object_size(length);

Klass* k = array_klass(n+dimension(), CHECK_0);

ArrayKlass* ak = ArrayKlass::cast(k);

objArrayOop o = (objArrayOop)Universe::heap()->array_allocate(ak, size, length,

/* do_zero */ true, CHECK_0);

// initialization to NULL not necessary, area already cleared

return o;

}

void ArrayKlass::array_klasses_do(void f(Klass* k, TRAPS), TRAPS) {

Klass* k = this;

// Iterate over this array klass and all higher dimensions

while (k != NULL) {

f(k, CHECK);

k = ArrayKlass::cast(k)->higher_dimension();

}

}

void ArrayKlass::array_klasses_do(void f(Klass* k)) {

Klass* k = this;

// Iterate over this array klass and all higher dimensions

while (k != NULL) {

f(k);

k = ArrayKlass::cast(k)->higher_dimension();

}

}

// JVM support

jint ArrayKlass::compute_modifier_flags(TRAPS) const {

return JVM_ACC_ABSTRACT | JVM_ACC_FINAL | JVM_ACC_PUBLIC;

}

// JVMTI support

jint ArrayKlass::jvmti_class_status() const {

return JVMTI_CLASS_STATUS_ARRAY;

}

void ArrayKlass::metaspace_pointers_do(MetaspaceClosure* it) {

Klass::metaspace_pointers_do(it);

ResourceMark rm;

log_trace(cds)(“Iter(ArrayKlass): %p (%s)”, this, external_name());

// need to cast away volatile

it->push((Klass**)&_higher_dimension);

it->push((Klass**)&_lower_dimension);

}

void ArrayKlass::remove_unshareable_info() {

Klass::remove_unshareable_info();

if (_higher_dimension != NULL) {

ArrayKlass *ak = ArrayKlass::cast(higher_dimension());

ak->remove_unshareable_info();

}

}

void ArrayKlass::remove_java_mirror() {

Klass::remove_java_mirror();

if (_higher_dimension != NULL) {

ArrayKlass *ak = ArrayKlass::cast(higher_dimension());

ak->remove_java_mirror();

}

}

void ArrayKlass::restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS) {

assert(loader_data == ClassLoaderData::the_null_class_loader_data(), “array classes belong to null loader”);

Klass::restore_unshareable_info(loader_data, protection_domain, CHECK);

// Klass recreates the component mirror also

if (_higher_dimension != NULL) {

ArrayKlass *ak = ArrayKlass::cast(higher_dimension());

ak->restore_unshareable_info(loader_data, protection_domain, CHECK);

}

}

// Printing

void ArrayKlass::print_on(outputStream* st) const {

assert(is_klass(), “must be klass”);

Klass::print_on(st);

}

void ArrayKlass::print_value_on(outputStream* st) const {

assert(is_klass(), “must be klass”);

for(int index = 0; index < dimension(); index++) {

st->print(“[]”);

}

}

void ArrayKlass::oop_print_on(oop obj, outputStream* st) {

assert(obj->is_array(), “must be array”);

Klass::oop_print_on(obj, st);

st->print_cr(” – length: %d”, arrayOop(obj)->length());

}

// Verification

void ArrayKlass::verify_on(outputStream* st) {

Klass::verify_on(st);

}

void ArrayKlass::oop_verify_on(oop obj, outputStream* st) {

guarantee(obj->is_array(), “must be array”);

arrayOop a = arrayOop(obj);

guarantee(a->length() >= 0, “array with negative length?”);

}



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