本文主要是介绍ConstantPool结构，对大家解决编程问题具有一定的参考价值，需要的程序猿们随着小编来一起学习吧！

结构图

                 本图来自揭秘Java虚拟机(JVM设计原理与实现)

数据存放源码

put

void slot_at_put(int which, CPSlot s) const {
    assert(is_within_bounds(which), "index out of bounds");
    assert(s.value() != 0, "Caught something");
    *(intptr_t*)&base()[which] = s.value();
  }
  intptr_t* obj_at_addr_raw(int which) const {
    assert(is_within_bounds(which), "index out of bounds");
    return (intptr_t*) &base()[which];
  }

  jint* int_at_addr(int which) const {
    assert(is_within_bounds(which), "index out of bounds");
    return (jint*) &base()[which];
  }

  jlong* long_at_addr(int which) const {
    assert(is_within_bounds(which), "index out of bounds");
    return (jlong*) &base()[which];
  }

  jfloat* float_at_addr(int which) const {
    assert(is_within_bounds(which), "index out of bounds");
    return (jfloat*) &base()[which];
  }

  jdouble* double_at_addr(int which) const {
    assert(is_within_bounds(which), "index out of bounds");
    return (jdouble*) &base()[which];
  }

 // For temporary use while constructing constant pool
  void klass_index_at_put(int which, int name_index) {
    tag_at_put(which, JVM_CONSTANT_ClassIndex);
    *int_at_addr(which) = name_index;
  }

  // Temporary until actual use
  void unresolved_klass_at_put(int which, Symbol* s) {
    release_tag_at_put(which, JVM_CONSTANT_UnresolvedClass);
    slot_at_put(which, s);
  }

  void method_handle_index_at_put(int which, int ref_kind, int ref_index) {
    tag_at_put(which, JVM_CONSTANT_MethodHandle);
    *int_at_addr(which) = ((jint) ref_index<<16) | ref_kind;
  }

  void method_type_index_at_put(int which, int ref_index) {
    tag_at_put(which, JVM_CONSTANT_MethodType);
    *int_at_addr(which) = ref_index;
  }

  void invoke_dynamic_at_put(int which, int bootstrap_specifier_index, int name_and_type_index) {
    tag_at_put(which, JVM_CONSTANT_InvokeDynamic);
    *int_at_addr(which) = ((jint) name_and_type_index<<16) | bootstrap_specifier_index;
  }

  void unresolved_string_at_put(int which, Symbol* s) {
    release_tag_at_put(which, JVM_CONSTANT_String);
    *symbol_at_addr(which) = s;
  }

  void int_at_put(int which, jint i) {
    tag_at_put(which, JVM_CONSTANT_Integer);
    *int_at_addr(which) = i;
  }

  void long_at_put(int which, jlong l) {
    tag_at_put(which, JVM_CONSTANT_Long);
    // *long_at_addr(which) = l;
    Bytes::put_native_u8((address)long_at_addr(which), *((u8*) &l));
  }

  void float_at_put(int which, jfloat f) {
    tag_at_put(which, JVM_CONSTANT_Float);
    *float_at_addr(which) = f;
  }

  void double_at_put(int which, jdouble d) {
    tag_at_put(which, JVM_CONSTANT_Double);
    // *double_at_addr(which) = d;
    // u8 temp = *(u8*) &d;
    Bytes::put_native_u8((address) double_at_addr(which), *((u8*) &d));
  }

  Symbol** symbol_at_addr(int which) const {
    assert(is_within_bounds(which), "index out of bounds");
    return (Symbol**) &base()[which];
  }

  void symbol_at_put(int which, Symbol* s) {
    assert(s->refcount() != 0, "should have nonzero refcount");
    tag_at_put(which, JVM_CONSTANT_Utf8);
    *symbol_at_addr(which) = s;
  }

  void string_at_put(int which, int obj_index, oop str) {
    resolved_references()->obj_at_put(obj_index, str);
  }

  // For temporary use while constructing constant pool
  void string_index_at_put(int which, int string_index) {
    tag_at_put(which, JVM_CONSTANT_StringIndex);
    *int_at_addr(which) = string_index;
  }

  void field_at_put(int which, int class_index, int name_and_type_index) {
    tag_at_put(which, JVM_CONSTANT_Fieldref);
    *int_at_addr(which) = ((jint) name_and_type_index<<16) | class_index;
  }

  void method_at_put(int which, int class_index, int name_and_type_index) {
    tag_at_put(which, JVM_CONSTANT_Methodref);
    *int_at_addr(which) = ((jint) name_and_type_index<<16) | class_index;
  }

  void interface_method_at_put(int which, int class_index, int name_and_type_index) {
    tag_at_put(which, JVM_CONSTANT_InterfaceMethodref);
    *int_at_addr(which) = ((jint) name_and_type_index<<16) | class_index;  // Not so nice
  }

  void name_and_type_at_put(int which, int name_index, int signature_index) {
    tag_at_put(which, JVM_CONSTANT_NameAndType);
    *int_at_addr(which) = ((jint) signature_index<<16) | name_index;  // Not so nice
  }

tags

Array<u1>* tags() const                   
{ return _tags; }

void tag_at_put(int which, jbyte t)          
{ tags()->at_put(which, t); } // 常量池类型标志

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