Java by API/java.lang/Runtime
Содержание
Runtime: addShutdownHook(Thread hook)
<source lang="java">
public class MainClass {
public static void main(String[] args) throws Exception {
Object f = new Object() {
public void finalize() {
System.out.println("Running finalize()");
}
};
Runtime.getRuntime().addShutdownHook(new Thread() {
public void run() {
System.out.println("Running Shutdown Hook");
}
});
f = null;
System.gc();
System.out.println("Calling System.exit()");
System.exit(0);
}
}
</source>
Runtime: availableProcessors()
<source lang="java">
public class Main {
public static void main(String[] args) {
Runtime runtime = Runtime.getRuntime();
int nrOfProcessors = runtime.availableProcessors();
System.out.println("Number of processors available to the Java Virtual Machine: "
+ nrOfProcessors);
}
} // Number of processors available to the Java Virtual Machine: 2
</source>
Runtime: exec(String[] command)
<source lang="java">
/*
* Output: * * * * */
public class MainClass {
public static void main(String args[]) {
Runtime r = Runtime.getRuntime();
Process p = null;
String cmd[] = { "notepad", "/java/src/java/lang/Runtime.java" };
try {
p = r.exec(cmd);
} catch (Exception e) {
System.out.println("error executing " + cmd[0]);
}
}
}
</source>
Runtime: exec(String command) (2)
<source lang="java">
/*
* Output: */
public class MainClass {
public static void main(String args[]) {
Runtime r = Runtime.getRuntime();
Process p = null;
try {
p = r.exec("notepad");
} catch (Exception e) {
System.out.println("Error executing notepad.");
}
}
}
</source>
Runtime: freeMemory()
<source lang="java">
/*
* Output:
Total memory is: 2031616 Initial free memory: 1774312 Free memory after garbage collection: 1875680 Free memory after allocation: 1715296 Memory used by allocation: 160384 Free memory after collecting discarded Integers: 1875680
*/
public class MainClass {
public static void main(String args[]) {
Runtime r = Runtime.getRuntime();
long mem1, mem2;
Integer someints[] = new Integer[10000];
System.out.println("Total memory is: " + r.totalMemory());
mem1 = r.freeMemory();
System.out.println("Initial free memory: " + mem1);
r.gc();
mem1 = r.freeMemory();
System.out.println("Free memory after garbage collection: " + mem1);
for (int i = 0; i < someints.length; i++)
someints[i] = new Integer(i); // allocate integers
mem2 = r.freeMemory();
System.out.println("Free memory after allocation: " + mem2);
System.out.println("Memory used by allocation: " + (mem1 - mem2));
for (int i = 0; i < someints.length; i++)
someints[i] = null;
r.gc(); // request garbage collection
mem2 = r.freeMemory();
System.out.println("Free memory after collecting" + " discarded Integers: "
+ mem2);
}
}
</source>
Runtime: gc()
<source lang="java">
/*
* Output:
Total memory is: 2031616 Initial free memory: 1774312 Free memory after garbage collection: 1875680 Free memory after allocation: 1715296 Memory used by allocation: 160384 Free memory after collecting discarded Integers: 1875680
*/
public class MainClass {
public static void main(String args[]) {
Runtime r = Runtime.getRuntime();
long mem1, mem2;
Integer someints[] = new Integer[10000];
System.out.println("Total memory is: " + r.totalMemory());
mem1 = r.freeMemory();
System.out.println("Initial free memory: " + mem1);
r.gc();
mem1 = r.freeMemory();
System.out.println("Free memory after garbage collection: " + mem1);
for (int i = 0; i < someints.length; i++)
someints[i] = new Integer(i); // allocate integers
mem2 = r.freeMemory();
System.out.println("Free memory after allocation: " + mem2);
System.out.println("Memory used by allocation: " + (mem1 - mem2));
for (int i = 0; i < someints.length; i++)
someints[i] = null;
r.gc(); // request garbage collection
mem2 = r.freeMemory();
System.out.println("Free memory after collecting" + " discarded Integers: "
+ mem2);
}
}
</source>
Runtime.getRuntime()
<source lang="java">
/*
* Output: * * * * */
public class MainClass {
public static void main(String args[]) {
Runtime r = Runtime.getRuntime();
Process p = null;
String cmd[] = { "notepad", "/java/src/java/lang/Runtime.java" };
try {
p = r.exec(cmd);
} catch (Exception e) {
System.out.println("error executing " + cmd[0]);
}
}
}
</source>
Runtime: maxMemory()
<source lang="java">
public class Main {
public static void main(String[] argv) throws Exception {
long heapSize = Runtime.getRuntime().totalMemory();
long heapMaxSize = Runtime.getRuntime().maxMemory();
long heapFreeSize = Runtime.getRuntime().freeMemory();
}
}
</source>
Runtime: totalMemory()
<source lang="java">
/*
* Output:
Total memory is: 2031616 Initial free memory: 1774312 Free memory after garbage collection: 1875680 Free memory after allocation: 1715296 Memory used by allocation: 160384 Free memory after collecting discarded Integers: 1875680
*/
public class MainClass {
public static void main(String args[]) {
Runtime r = Runtime.getRuntime();
long mem1, mem2;
Integer someints[] = new Integer[10000];
System.out.println("Total memory is: " + r.totalMemory());
mem1 = r.freeMemory();
System.out.println("Initial free memory: " + mem1);
r.gc();
mem1 = r.freeMemory();
System.out.println("Free memory after garbage collection: " + mem1);
for (int i = 0; i < someints.length; i++)
someints[i] = new Integer(i); // allocate integers
mem2 = r.freeMemory();
System.out.println("Free memory after allocation: " + mem2);
System.out.println("Memory used by allocation: " + (mem1 - mem2));
for (int i = 0; i < someints.length; i++)
someints[i] = null;
r.gc(); // request garbage collection
mem2 = r.freeMemory();
System.out.println("Free memory after collecting" + " discarded Integers: "
+ mem2);
}
}
</source>
