String类的转换功能

 

 

package cn.itcast.Demo4;

public class Test3 {
    public static void main(String[] args) {
        //定义一个字符串
        String s1 = "abc";
        //byte[] getBytes(); 将字符串转换成字节数组
        byte[] bys = s1.getBytes(); //97,98,99
        for (int i = 0 ; i<bys.length;i++){
            System.out.println(bys[i]);
        }
        System.out.println("=====================");

        //char[] toCharArray();将字符串转换成字符数组
        char[] chs = s1.toCharArray(); //'a' 'b' 'c'
        for (int i = 0; i <chs.length ; i++) {
            System.out.println(chs[i]);
        }
        System.out.println("=====================");

        //static String valueOf(..);将指定类型数据转换成字符串
        //整数123-->字符串“123”  此为静态方法，可以直接调用
        String s2 = String.valueOf(123);
        System.out.println(s2+4); //1234
        //在实际开发中，上述的方式基本上都会用下边的这行代码替代
        String s3 = "" + 123 ;
        System.out.println(s3 + 4);
        System.out.println("=====================");

        //String replace(old,new); 将指定字符（串）替换成新的字符（串）
        String s4 = "acc acc acc";
        //'d' 替换'c'
        String s5 = s4.replace('c','d');
        System.out.println("s5:"+s5);
        System.out.println("=====================");

        //String[] split(String);切割字符串，返回切割后的字符串数据，原字符串不变
        //将字符串s4，按照空格进行切割
        //"acc acc acc"---->“acc” "acc" "acc"
        String[] arr = s4.split(" ");
        for (int i = 0; i <arr.length ; i++) {
            System.out.println(arr[i]);
        }

        System.out.println("=====================");
        
        //String trim()去掉字符串两端的空白字符
        String s6 = " a b c ";
        String s7 = s6.trim();//用户输入密码，一般需要用trim(()
        System.out.println("s6:"+s6);
        System.out.println("s7:"+s7);

    }
}