151010

//字符串
        
        String str = "aa";
        
        char c = 'd';
        
        int j = 1000;
        
        String st = new String("abc");
        
        char[] cc = {'a','b'};
        
        String str2 = new String(cc);
        
        System.out.println("str2 = " + str2);
        
        //连接字符串 +
        
        System.out.println("st + str2 + j = " + st  + str2 + j);
        
        // 99乘法表
        
        int [] a = new int[5];
        
        int l = a.length;//是属性
        
        int g = st.length();//是方法
        
        System.out.println("st.length() = "+ g);
        
        //查找
        
        int sy = st.indexOf("");
        
        System.out.println("st.indexOf(\"\") = " + sy);
        
        int sy1 = st.lastIndexOf("bc");
        
        System.out.println("st.LastIndexOf(\"\") = " + sy1);
        
        //取出字符
        
        System.out.println("charAt = " + st.charAt(2));
        
        //截取字符串
        
        System.out.println("substringf = " + st.charAt(1));
        
        //字符串 去除空格
        
        String str3 = "  abc def gh  ";
        
        System.out.println("str3.trim() =#" + str3.trim() + "#");
        
        str3 = str3.trim();
        
        System.out.println("str3 =#" + str3 + "#");
        
        //替换
        
        str3 = str3.replace("", "");
        
        System.out.println("str3.replace() =#" + str3 +"#");
        
        str3 = str3.replace("bc", "kk");
        
        System.out.println("str3.replace() =#" + str3 +"#");
        
        //判断字符串开始和结尾
        
        System.out.println("str3.startsWith() = " + str3.startsWith("ab"));
        
        String a1 = new String("aaa");
        
        String a2 = new String("aAa");
        
        System.out.println("a1 == a2 = " + a1 == a2);//比较的是内存地址
        
        System.out.println("a1.equals(a2) = " +a1.equals(a2));
        
        System.out.println("a1.equalsIgnoreCase(a2) = " +a1.equalsIgnoreCase(a2));
        
        //按字典顺序比较 Unicode的值
        
        System.out.println("compareTo = " + a1.compareTo(a2));
        
        //大小写转换
        
        System.out.println("a1.toUpperCase = " + a1.toUpperCase());
        
        a1.toLowerCase();
        
        //字符串分隔 aa;bb;cc;dd;
        
        String fg = "aa;bbb;cc,ccc;sdd5sss";
        
        String[] arr = fg.split(";");
        
        String[] arr2 = fg.split(";|5");// "."不能作为分隔符
        
        String[] arr1 = fg.split(";",3);
        
        for(String f : arr2)
        {
            System.out.println(f);
        }
        
        //格式化字符串 日期时间 静态方法
        //String.format(格式符，要被格式化的对象)
        
        Date dt = new Date();//实例化日期，生成当前日期
        
        System.out.println(String.format("%tF", dt));
        
        System.out.println(String.format("%tT", dt));
        
        System.out.println(String.format("%tF", dt) + "" + String.format("%tT", dt));
        
        System.out.println("200的十六进制 = " + String.format("%x",200));
        
        System.out.println("特定换行 " + String.format("%n") + "换行");