Java-常用类-其他类

System类

代码示例：

@Test
public void test1() {
    String javaVersion = System.getProperty("java.version");
    System.out.println("java的version:" + javaVersion);

    String javaHome = System.getProperty("java.home");
    System.out.println("java的home:" + javaHome);

    String osName = System.getProperty("os.name");
    System.out.println("os的name:" + osName);

    String osVersion = System.getProperty("os.version");
    System.out.println("os的version:" + osVersion);

    String userName = System.getProperty("user.name");
    System.out.println("user的name:" + userName);

    String userHome = System.getProperty("user.home");
    System.out.println("user的home:" + userHome);

    String userDir = System.getProperty("user.dir");
    System.out.println("user的dir:" + userDir);

}

输出：

Math类

BigInteger与BigDecimal

BigInteger类——>对应整型

BigDecimal类——>对应浮点型

代码示例:

@Test
    public void test2() {
        BigInteger bi = new BigInteger("1243324112234324324325235245346567657653");
        BigDecimal bd = new BigDecimal("12435.351");
        BigDecimal bd2 = new BigDecimal("11");
        System.out.println(bi);
//         System.out.println(bd.divide(bd2));
        System.out.println(bd.divide(bd2, BigDecimal.ROUND_HALF_UP));
        System.out.println(bd.divide(bd2, 25, BigDecimal.ROUND_HALF_UP));

    }