RamUsageEstimator (Lucene 4.9.1 API)

java.lang.Object
- org.apache.lucene.util.RamUsageEstimator

```
public final class RamUsageEstimator
extends Object
```
Estimates the size (memory representation) of Java objects.

See Also:
shallowSizeOf(Object), shallowSizeOfInstance(Class)
NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

static class RamUsageEstimator.JvmFeature
JVM diagnostic features.

Nested Classes
Modifier and Type	Class and Description
`static class`	`RamUsageEstimator.JvmFeature` JVM diagnostic features.

Field Summary

Fields
Modifier and Type	Field and Description
`static String`	`JVM_INFO_STRING` JVM info string for debugging and reports.
`static int`	`NUM_BYTES_ARRAY_HEADER` Number of bytes to represent an array header (no content, but with alignments).
`static int`	`NUM_BYTES_BOOLEAN`
`static int`	`NUM_BYTES_BYTE`
`static int`	`NUM_BYTES_CHAR`
`static int`	`NUM_BYTES_DOUBLE`
`static int`	`NUM_BYTES_FLOAT`
`static int`	`NUM_BYTES_INT`
`static int`	`NUM_BYTES_LONG`
`static int`	`NUM_BYTES_OBJECT_ALIGNMENT` A constant specifying the object alignment boundary inside the JVM.
`static int`	`NUM_BYTES_OBJECT_HEADER` Number of bytes to represent an object header (no fields, no alignments).
`static int`	`NUM_BYTES_OBJECT_REF` Number of bytes this jvm uses to represent an object reference.
`static int`	`NUM_BYTES_SHORT`
`static long`	`ONE_GB` One gigabyte bytes.
`static long`	`ONE_KB` One kilobyte bytes.
`static long`	`ONE_MB` One megabyte bytes.

Method Summary

Methods
Modifier and Type	Method and Description
`static long`	`alignObjectSize(long size)` Aligns an object size to be the next multiple of `NUM_BYTES_OBJECT_ALIGNMENT`.
`static EnumSet<RamUsageEstimator.JvmFeature>`	`getSupportedFeatures()` Return the set of supported JVM features that improve the estimation.
`static EnumSet<RamUsageEstimator.JvmFeature>`	`getUnsupportedFeatures()` Return the set of unsupported JVM features that improve the estimation.
`static String`	`humanReadableUnits(long bytes)` Returns `size` in human-readable units (GB, MB, KB or bytes).
`static String`	`humanReadableUnits(long bytes, DecimalFormat df)` Returns `size` in human-readable units (GB, MB, KB or bytes).
`static boolean`	`isSupportedJVM()` Returns true, if the current JVM is fully supported by `RamUsageEstimator`.
`static long`	`shallowSizeOf(Object obj)` Estimates a "shallow" memory usage of the given object.
`static long`	`shallowSizeOf(Object[] arr)` Returns the shallow size in bytes of the Object[] object.
`static long`	`shallowSizeOfInstance(Class<?> clazz)` Returns the shallow instance size in bytes an instance of the given class would occupy.
`static long`	`sizeOf(boolean[] arr)` Returns the size in bytes of the boolean[] object.
`static long`	`sizeOf(byte[] arr)` Returns the size in bytes of the byte[] object.
`static long`	`sizeOf(char[] arr)` Returns the size in bytes of the char[] object.
`static long`	`sizeOf(double[] arr)` Returns the size in bytes of the double[] object.
`static long`	`sizeOf(float[] arr)` Returns the size in bytes of the float[] object.
`static long`	`sizeOf(int[] arr)` Returns the size in bytes of the int[] object.
`static long`	`sizeOf(Long value)` Return the size of the provided `Long` object, returning 0 if it is cached by the JVM and its shallow size otherwise.
`static long`	`sizeOf(long[] arr)` Returns the size in bytes of the long[] object.
`static long`	`sizeOf(short[] arr)` Returns the size in bytes of the short[] object.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - JVM_INFO_STRING
```
public static final String JVM_INFO_STRING
```
    JVM info string for debugging and reports.
  - ONE_KB
```
public static final long ONE_KB
```
    One kilobyte bytes.
    
    See Also:
    Constant Field Values
  - ONE_MB
```
public static final long ONE_MB
```
    One megabyte bytes.
    
    See Also:
    Constant Field Values
  - ONE_GB
```
public static final long ONE_GB
```
    One gigabyte bytes.
    
    See Also:
    Constant Field Values
  - NUM_BYTES_BOOLEAN
```
public static final int NUM_BYTES_BOOLEAN
```
    See Also:
    Constant Field Values
  - NUM_BYTES_BYTE
```
public static final int NUM_BYTES_BYTE
```
    See Also:
    Constant Field Values
  - NUM_BYTES_CHAR
```
public static final int NUM_BYTES_CHAR
```
    See Also:
    Constant Field Values
  - NUM_BYTES_SHORT
```
public static final int NUM_BYTES_SHORT
```
    See Also:
    Constant Field Values
  - NUM_BYTES_INT
```
public static final int NUM_BYTES_INT
```
    See Also:
    Constant Field Values
  - NUM_BYTES_FLOAT
```
public static final int NUM_BYTES_FLOAT
```
    See Also:
    Constant Field Values
  - NUM_BYTES_LONG
```
public static final int NUM_BYTES_LONG
```
    See Also:
    Constant Field Values
  - NUM_BYTES_DOUBLE
```
public static final int NUM_BYTES_DOUBLE
```
    See Also:
    Constant Field Values
  - NUM_BYTES_OBJECT_REF
```
public static final int NUM_BYTES_OBJECT_REF
```
    Number of bytes this jvm uses to represent an object reference.
  - NUM_BYTES_OBJECT_HEADER
```
public static final int NUM_BYTES_OBJECT_HEADER
```
    Number of bytes to represent an object header (no fields, no alignments).
  - NUM_BYTES_ARRAY_HEADER
```
public static final int NUM_BYTES_ARRAY_HEADER
```
    Number of bytes to represent an array header (no content, but with alignments).
  - NUM_BYTES_OBJECT_ALIGNMENT
```
public static final int NUM_BYTES_OBJECT_ALIGNMENT
```
    A constant specifying the object alignment boundary inside the JVM. Objects will always take a full multiple of this constant, possibly wasting some space.
- Method Detail
  - isSupportedJVM
```
public static boolean isSupportedJVM()
```
    Returns true, if the current JVM is fully supported by RamUsageEstimator. If this method returns false you are maybe using a 3rd party Java VM that is not supporting Oracle/Sun private APIs. The memory estimates can be imprecise then (no way of detecting compressed references, alignments, etc.). Lucene still tries to use sensible defaults.
  - alignObjectSize
```
public static long alignObjectSize(long size)
```
    Aligns an object size to be the next multiple of NUM_BYTES_OBJECT_ALIGNMENT.
  - sizeOf
```
public static long sizeOf(Long value)
```
    Return the size of the provided Long object, returning 0 if it is cached by the JVM and its shallow size otherwise.
  - sizeOf
```
public static long sizeOf(byte[] arr)
```
    Returns the size in bytes of the byte[] object.
  - sizeOf
```
public static long sizeOf(boolean[] arr)
```
    Returns the size in bytes of the boolean[] object.
  - sizeOf
```
public static long sizeOf(char[] arr)
```
    Returns the size in bytes of the char[] object.
  - sizeOf
```
public static long sizeOf(short[] arr)
```
    Returns the size in bytes of the short[] object.
  - sizeOf
```
public static long sizeOf(int[] arr)
```
    Returns the size in bytes of the int[] object.
  - sizeOf
```
public static long sizeOf(float[] arr)
```
    Returns the size in bytes of the float[] object.
  - sizeOf
```
public static long sizeOf(long[] arr)
```
    Returns the size in bytes of the long[] object.
  - sizeOf
```
public static long sizeOf(double[] arr)
```
    Returns the size in bytes of the double[] object.
  - shallowSizeOf
```
public static long shallowSizeOf(Object[] arr)
```
    Returns the shallow size in bytes of the Object[] object.
  - shallowSizeOf
```
public static long shallowSizeOf(Object obj)
```
    Estimates a "shallow" memory usage of the given object. For arrays, this will be the memory taken by array storage (no subreferences will be followed). For objects, this will be the memory taken by the fields. JVM object alignments are also applied.
  - shallowSizeOfInstance
```
public static long shallowSizeOfInstance(Class<?> clazz)
```
    Returns the shallow instance size in bytes an instance of the given class would occupy. This works with all conventional classes and primitive types, but not with arrays (the size then depends on the number of elements and varies from object to object).
    
    Throws:
    
    IllegalArgumentException - if clazz is an array class.
    See Also:
    shallowSizeOf(Object)
  - getUnsupportedFeatures
```
public static EnumSet<RamUsageEstimator.JvmFeature> getUnsupportedFeatures()
```
    Return the set of unsupported JVM features that improve the estimation.
  - getSupportedFeatures
```
public static EnumSet<RamUsageEstimator.JvmFeature> getSupportedFeatures()
```
    Return the set of supported JVM features that improve the estimation.
  - humanReadableUnits
```
public static String humanReadableUnits(long bytes)
```
    Returns size in human-readable units (GB, MB, KB or bytes).
  - humanReadableUnits
```
public static String humanReadableUnits(long bytes,
                        DecimalFormat df)
```
    Returns size in human-readable units (GB, MB, KB or bytes).

Class RamUsageEstimator

Nested Class Summary

Field Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

JVM_INFO_STRING

ONE_KB

ONE_MB

ONE_GB

NUM_BYTES_BOOLEAN

NUM_BYTES_BYTE

NUM_BYTES_CHAR

NUM_BYTES_SHORT

NUM_BYTES_INT

NUM_BYTES_FLOAT

NUM_BYTES_LONG

NUM_BYTES_DOUBLE

NUM_BYTES_OBJECT_REF

NUM_BYTES_OBJECT_HEADER

NUM_BYTES_ARRAY_HEADER

NUM_BYTES_OBJECT_ALIGNMENT

Method Detail

isSupportedJVM

alignObjectSize

sizeOf

sizeOf

sizeOf

sizeOf

sizeOf

sizeOf

sizeOf

sizeOf

sizeOf

shallowSizeOf

shallowSizeOf

shallowSizeOfInstance

getUnsupportedFeatures

getSupportedFeatures

humanReadableUnits

humanReadableUnits