String与其他类型的转换

String与基本数据类型、包装类

//String --> 基本数据类型、包装类:调用包装类的静态方法：parseXxx(str)
//基本数据类型、包装类-->String:调用String重载的valueOf(xxx)
    @Test
    public void test1(){
        String str1 = "123";
        int num = Integer.parseInt(str1);
        String str2 = String.valueOf(num);
        String str3 = num + ""; //堆
        System.out.println(str1 == str3);//false

    }

String与char[]

//String --> char[]:调用toCharArray()
//char[] --> String:调用String构造器
    @Test
    public void test2(){
        String str1 = "abc123";
        char[] charArray = str1.toCharArray();
        for(int i = 0; i < charArray.length;i++){
            System.out.println(charArray[i]);
        }

        char[] arr = new char[]{'h','e','l','l','o'};
        String str2 = new String(arr);
        System.out.println(str2);

    }

结果

a
b
c
1
2
3
hello

String 与 byte[]之间的转换

//String --> byte[]:调用String的getBytes()
//byte[] --> String:调用String的构造器
//编码：字符串-->字节
//解码：字节-->字符串
    @Test
    public void test3() throws UnsupportedEncodingException {
        String str1 = "abc123中国";
        byte[] bytes = str1.getBytes();
        System.out.println(Arrays.toString(bytes));

        byte[] gbks = str1.getBytes("gbk");
        System.out.println(Arrays.toString(gbks));

        String str2 = new String(bytes);
        System.out.println(str2);
        String str3 = new String(gbks);
        System.out.println(str3);
        String str4 = new String(gbks,"gbk");
        System.out.println(str4);

    }

结果

[97, 98, 99, 49, 50, 51, -28, -72, -83, -27, -101, -67]
[97, 98, 99, 49, 50, 51, -42, -48, -71, -6]
abc123中国
abc123�й�
abc123中国