1、Runtime：

1 public class RuntimeDemo { 2  3     public static void main(String[] args) { 4         Runtime runtime=Runtime.getRuntime(); 5         System.out.println("最大容量"+runtime.maxMemory()/1024/1024+"MBytes"); 6         System.out.println("CPUs : "+runtime.availableProcessors()); 7         System.out.println("Free Memory: "+runtime.freeMemory()/1024/1024+"MBytes"); 8         System.out.println("Total Memory:"+runtime.totalMemory()/1024/1024+"MBytes"); 9     }10 11 }

2、Properties()：

1 import java.util.Enumeration; 2 import java.util.Properties; 3  4 public class SysInfo { 5     public static void main(String[] args) { 6         Properties properties=System.getProperties();//getProperties()用于获取当前系统的全部属性 7         Enumeration
      propertyNames=properties.propertyNames(); 8         while(propertyNames.hasMoreElements()) { 9             String key=(String)propertyNames.nextElement();10             String value=System.getProperty(key);//System.getProperty()获得指定键描述的系统属性11             System.out.println(key+"---->"+value);12         }13 //        System.out.println("Java Version:"+System.getProperty("java.version"));14 //        System.out.println("OS Name:"+System.getProperty("os.name"));15 //        System.out.println("OS Version:"+System.getProperty("os.version"));16     }17 }

3、ArrayCopy

1 import java.util.Arrays; 2  3 public class ArrayCopy { 4  5     public static void main(String[] args) { 6         int[] data1 = {1, 2, 3, 4,5 }; 7         int[] data2 = new int[10]; 8          9         System.arraycopy(data1, 2, data2, 2, 3);10         11         System.out.println(Arrays.toString(data2));12     }13 14 }15 //结果显示：[0, 0, 3, 4, 5, 0, 0, 0, 0, 0]