4.3.2
The Class
Object
TYPES, VALUES, AND VARIABLES
The example program:
class Value { int val; }
class Test {
public static void main(String[] args) {
int i1 = 3;
int i2 = i1;
i2 = 4;
System.out.print("i1==" + i1);
System.out.println(" but i2==" + i2);
Value v1 = new Value();
v1.val = 5;
Value v2 = v1;
v2.val = 6;
System.out.print("v1.val==" + v1.val);
System.out.println(" and v2.val==" + v2.val);
}
}
produces the output:
i1==3 but i2==4
v1.val==6 and v2.val==6
because
v1.val
 and
v2.val
 reference the same instance variable ( 4.5.3) in the
one
Value
 object created by the only
new
 expression, while
i1
 and
i2
 are differ 
ent variables.
See  10 and  15.9 for examples of the creation and use of arrays.
Each object has an associated lock ( 17.13), which is used by
synchronized
methods ( 8.4.3) and the
synchronized
 statement ( 14.17) to provide control
over concurrent access to state by multiple threads ( 17.12,  20.20).
4.3.2   The Class
Object
The standard class
Object
 is a superclass ( 8.1) of all other classes. A variable of
type
Object
 can hold a reference to any object, whether it is an instance of a class
or an array ( 10). All class and array types inherit the methods of class
Object
,
which are summarized here and completely specified in  20.1:
package java.lang;
public class Object {
public final Class getClass() {
. . .
 }
public String toString() {
. . .
 }
public boolean equals(Object obj) {
. . .
 }
public int hashCode() {
. . .
 }
protected Object clone()
throws CloneNotSupportedException {
. . .
 }
40






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