Java.lang System

1 Java.lang System介绍

java.lang.System 类包含一些有用的类字段和方法。它不能被实例化。通过系统提供的工具：

• 标准输出

• 错误输出流

• 标准输入和访问外部定义的属性和环境变量。

• 一种实用程序方法，用于快速复制数组的一部分。

• 加载文件和库文件的方法

2 Java.lang System声明

public final class System
   extends Object

3 Java.lang System方法

4  Java.lang System案例1

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
import java.lang.*;  
public class SystemArrayCopyExample1 {  
  
    public static void main(String[] args) {  
        String a[]= {"A","B","B","H","A","M"}; //source array  
        String b[]= {"S","H","U","N","U","L","L","J","A","D","O","N"};  //destination array  
        String src[],dest[];  
int srcPos,destPos,length;  
src=a;  
srcPos=2;  
dest=b;  
destPos=3;  
length=4;  
        System.out.print("Source array:");  
for(int i=0;i<src.length;i++) {System.out.print(a[i]);}  
        System.out.println();  
        System.out.print("Destination array:");  
for(int i=0;i<src.length;i++) {System.out.print(b[i]);}  
        System.out.println();  
        System.out.println("Source Position:"+srcPos);  
        System.out.println("Destination Position:"+destPos);  
        System.out.println("Length:"+length);  
        System.arraycopy(src, srcPos, dest, destPos, length); //use of arraycopy() method  
        System.out.println("Destination array after use of arraycopy()");  
for(int i=0;i<b.length;i++)  
        {  
    System.out.print(b[i]);  
        }  
    }  
  
} 

输出结果为：

Source array:ABBHAM
Destination array:SHUNUL
Source Position:2
Destination Position:3
Length:4
Destination array after use of arraycopy()
SHUBHAMJADON

5  Java.lang System案例2

package com.yiidian;

/**
 * 一点教程网： http://www.yiidian.com
 */
public class SystemCurrentTimeMillisExample2 {  
  
    public static void main(String[] args) {  
        System.out.println("Current time in millisecond");  
        System.out.println(System.currentTimeMillis()); //method of calling current time in millisecond  
    }  
}  

输出结果为：

Current time in millisecond
1532262046724