包装数据类型浅谈看下面代码推断其输出结果```更多技术资讯可关注：gzitcast

看下面代码推断其输出结果 ```

public static void main(String[] args) {
Integer a = 18;
Integer b = 18;
Integer c = 200;
Integer d = 200;
System.out.println(a == b);
System.out.println(c == d);
}

```

有老铁肯定会说，都是ture或者都是false ，那恭喜你，完美的进套了。

也有老铁，直接运行代码后发现结果是true false ，这下老铁就疑惑了，都是一样的赋值方式，怎么还有两样的结果呢，咋回事呢。

看源码

```

/**
* Returns an {
@code
Integer} instance representing the specified
* {
@code
int} value. If a new {
@code
Integer} instance is not
* required, this method should generally be used in preference to
* the constructor {
@link
#Integer(int)}, as this method is likely
* to yield significantly better space and time performance by
* caching frequently requested values.
*
* This method will always cache values in the range -128 to 127,
* inclusive, and may cache other values outside of this range.
*
*
@param
i
an {
@code
int} value.
*
@return
an {
@code
Integer} instance representing {
@code
i}.
*
@since
1.5
*/
public static
Integer valueOf(
int
i) {

if
(i >= IntegerCache.
low
&& i <= IntegerCache.
high
)

return
IntegerCache.
cache
[i + (-IntegerCache.
low
)];

return new
Integer(i);
}

/**
* Cache to support the object identity semantics of autoboxing for values between
* -128 and 127 (inclusive) as required by JLS.
*
* The cache is initialized on first usage. The size of the cache
* may be controlled by the {
@code
-XX:AutoBoxCacheMax=
<size>
} option.
* During VM initialization, java.lang.Integer.IntegerCache.high property
* may be set and saved in the private system properties in the
* sun.misc.VM class.
*/

private static class
IntegerCache {

static final int
low
= -
128
;

static final int
high
;

static final
Integer
cache
[];

static
{

// high value may be configured by property

int
h =
127
;
String integerCacheHighPropValue =
sun.misc.VM.getSavedProperty(
"java.lang.Integer.IntegerCache.high"
);

if
(integerCacheHighPropValue !=
null
) {

try
{

int
i = parseInt(integerCacheHighPropValue);
i = Math.max(i,
127
);

// Maximum array size is Integer.MAX_VALUE

h = Math.min(i, Integer.
MAX_VALUE
- (-
low
) -
1
);
}
catch
( NumberFormatException nfe) {

// If the property cannot be parsed into an int, ignore it.

}
}

high
= h;

cache
=
new
Integer[(
high
-
low
) +
1
];

int
j =
low
;

for
(
int
k =
0
; k <
cache
.
length
; k++)

cache
[k] =
new
Integer(j++);

// range [-128, 127] must be interned (JLS7 5.1.7)

assert
IntegerCache.
high
>=
127
;
}

private
IntegerCache() {}
}
```从上面的源码可以看到，他有一个缓冲区,-18---127 所以 200是不在缓冲区的，而18是在缓冲区的，所以结果可以理解了。今天就到这下次再扯。

更多技术资讯可关注：gzitcast