Java的常用类 System类 Math类 BigInteger 和 BigDecimal类

1.System 类

 

 

 

public void test(){
        String javaVersion = System.getProperty("java.version");
        System.out.println(javaVersion);
        String javaHome = System.getProperty("java.home");
        System.out.println(javaHome);
        String osName = System.getProperty("os.name");
        System.out.println(osName);
        String osVersion = System.getProperty("os.version");
        System.out.println(osVersion);
        String userName = System.getProperty("user.name");
        System.out.println(userName);
        String userHome = System.getProperty("user.home");
        System.out.println(userHome);
        String userDir = System.getProperty("user.dir");
        System.out.println(userDir);


    }

 

2.Math类

 

 

3.BigInteger类

 

 

 

4.BigDecimal类