Java面试题之六

package com.lovo;  
  
public class TestDot2 {  
    // 方法1  
    public void test1(double c) {  
        java.text.DecimalFormat df = new java.text.DecimalFormat("#.##");  
        System.out.println(df.format(c));  
    }  
  
    // 方法2  
    public void test2(double c) {  
  
        java.math.BigDecimal bd = new java.math.BigDecimal(String.valueOf(c));  
        bd = bd.setScale(2, java.math.BigDecimal.ROUND_HALF_UP);  
        System.out.println(bd);  
    }  
  
    // 方法3  
    public void test3(double c) {  
        long l1 = Math.round(c * 100); // 四舍五入  
        double ret = l1 / 100.0; // 注意：使用 100.0 而不是 100  
        System.out.println(ret);  
    }  
  
    public static void main(String[] args) {  
        double c = 3.056;  
        TestDot2 td2 = new TestDot2();  
        td2.test1(c);  
        // td2.test2(c);  
        // td2.test3(c);  
    }  
}  

package com.lovo;  
  
import java.util.Calendar;  
  
public class Test {  
  
    public static void main(String[] args) {  
        Calendar c = Calendar.getInstance();  
        c.set(Calendar.YEAR, 2004);  
        c.set(Calendar.MONTH, 11);  
        c.set(Calendar.DAY_OF_MONTH, 30);  
        System.out.println("输入的日期是：" + c.get(Calendar.YEAR) + "-"  
                + (c.get(Calendar.MONTH) + 1) + "-"  
                + c.get(Calendar.DAY_OF_MONTH));  
        judgeIsLastDay(c);  
        getLastDay(c);  
    }  
  
    /** 
     * 判断某个日期是不是当月的最后一天 
     *  
     * @param c 
     */  
    private static void judgeIsLastDay(Calendar c) {  
        Calendar c1 = (Calendar) c.clone();  
        c.add(Calendar.DAY_OF_MONTH, 1);  
        if (c.get(Calendar.MONTH) != c1.get(Calendar.MONTH)) {  
            System.out.println("你输入的日期是当月最后一天");  
        } else {  
            System.out.println("你输入的日期不是当月最后一天");  
        }  
    }  
  
    /** 
     * 获取某个日期所在月份的最后一天 
     *  
     * @param c 
     */  
    private static void getLastDay(Calendar c) {  
        c.add(Calendar.MONTH, 1);  
        c.set(Calendar.DAY_OF_MONTH, 1);  
        c.add(Calendar.DAY_OF_MONTH, -1);  
        System.out.println("当月最后一天的日期是：" + c.get(Calendar.YEAR) + "-"  
                + (c.get(Calendar.MONTH) + 1) + "-"  
                + c.get(Calendar.DAY_OF_MONTH));  
    }  
}