Java中System类的相关应用

1、Runtime：

 public class RuntimeDemo {

     public static void main(String[] args) {
         Runtime runtime=Runtime.getRuntime();
         System.out.println("最大容量"+runtime.maxMemory()/1024/1024+"MBytes");
         System.out.println("CPUs : "+runtime.availableProcessors());
         System.out.println("Free Memory: "+runtime.freeMemory()/1024/1024+"MBytes");
         System.out.println("Total Memory:"+runtime.totalMemory()/1024/1024+"MBytes");
     }

 }

2、Properties()：

 import java.util.Enumeration;
 import java.util.Properties;

 public class SysInfo {
     public static void main(String[] args) {
         Properties properties=System.getProperties();//getProperties()用于获取当前系统的全部属性
         Enumeration<?> propertyNames=properties.propertyNames();
         while(propertyNames.hasMoreElements()) {
             String key=(String)propertyNames.nextElement();
             String value=System.getProperty(key);//System.getProperty()获得指定键描述的系统属性
             System.out.println(key+"---->"+value);
         }
 //        System.out.println("Java Version:"+System.getProperty("java.version"));
 //        System.out.println("OS Name:"+System.getProperty("os.name"));
 //        System.out.println("OS Version:"+System.getProperty("os.version"));
     }
 }

3、ArrayCopy

 import java.util.Arrays;

 public class ArrayCopy {

     public static void main(String[] args) {
         int[] data1 = {1, 2, 3, 4,5 };
         int[] data2 = new int[10];

         System.arraycopy(data1, 2, data2, 2, 3);

         System.out.println(Arrays.toString(data2));
     }

 }
 //结果显示：[0, 0, 3, 4, 5, 0, 0, 0, 0, 0]