1、String类

/*

 * 构造方法：

 * public String():空构造

 * public String(byte[] bytes):把字节数组转成字符串

 * public String(byte[] bytes,int index,int length):把字节数组的一部分转成字符串

 * public String(char[] value):把字符数组转成字符串

 * public String(char[] value,int index,int count):把字符数组的一部分转成字符串

 * public String(String original):把字符串常量值转成字符串

 *      (注意：这里的index是从1算起的)

 * 字符串的方法：

 * public int length()：返回此字符串的长度。

 */

public class StringDemo {

public static void main(String[] args) {

// public String():空构造

String s1 = new String();

System.out.println("s1:" + s1);

System.out.println("s1.length():" + s1.length());

System.out.println("--------------------------");

// public String(byte[] bytes):把字节数组转成字符串

byte[] bys = { 97, 98, 99, 100, 101 };

String s2 = new String(bys);

System.out.println("s2:" + s2);

System.out.println("s2.length():" + s2.length());

System.out.println("--------------------------");

// public String(byte[] bytes,int index,int length):把字节数组的一部分转成字符串

// 我想得到字符串"bcd"

String s3 = new String(bys, 1, 3);

System.out.println("s3:" + s3);

System.out.println("s3.length():" + s3.length());

System.out.println("--------------------------");

// public String(char[] value):把字符数组转成字符串

char[] chs = { 'a', 'b', 'c', 'd', 'e', '爱', '林', '亲' };

String s4 = new String(chs);

System.out.println("s4:" + s4);

System.out.println("s4.length():" + s4.length());

System.out.println("--------------------------");

// public String(char[] value,int index,int count):把字符数组的一部分转成字符串

String s5 = new String(chs, 2, 4);

System.out.println("s5:" + s5);

System.out.println("s5.length():" + s5.length());

System.out.println("--------------------------");

//public String(String original):把字符串常量值转成字符串

String s6 = new String("abcde");

System.out.println("s6:" + s6);

System.out.println("s6.length():" + s6.length());

System.out.println("--------------------------");

//字符串字面值"abc"也可以看成是一个字符串对象。

String s7 = "abcde";

System.out.println("s7:"+s7);

System.out.println("s7.length():"+s7.length());

}

}

//执行结果如下：

s1:
s1.length():0
--------------------------
s2:abcde
s2.length():5
--------------------------
s3:bcd
s3.length():3
--------------------------
s4:abcde爱林亲
s4.length():8
--------------------------
s5:cde爱
s5.length():4
--------------------------
s6:abcde
s6.length():5
--------------------------
s7:abcde
s7.length():5