回顾JavaSE（2）-String（1）API构造方法

温故而知新，在Android开发的道路上越走越远的同时，不能忘了JavaSE。

String，最常用的类，没有之一。

先看最好的教材，官方API文档。

public final class String
extends Object
implements Serializable, Comparable<String>, CharSequence

The

String

class represents character strings. All string literals in Java programs, such as

"abc"

, are implemented as instances of this class.

Strings are constant; their values cannot be changed after they are created. String buffers support mutable strings. Because String objects are immutable they can be shared. For example:

String str = "abc";

is equivalent to:

char data[] = {'a', 'b', 'c'};
String str = new String(data);

String类概述
•字符串是由多个字符组成的一串数据(字符序列)
•字符串可以看成是字符数组

它的构造方法很多，我们重点看这几个：

构造方法：
•public String()
•public String(byte[] bytes)
•public String(byte[] bytes,int offset,int length)
•public String(char[] value)
•public String(char[] value,int offset,int count)
•public String(String original)

先重点看它里面的length方法：

public int length()

Returns the length of this string. The length is equal to the number ofUnicode code units in the string.
Specified by:

length

in interface

CharSequence

Returns:the length of the sequence of characters represented by this object.

是时候看一波源代码：

public class StringTest {

/**
* @param args
* 权兴权意-20160919
* 字符串：多个字符组成的一串数据，也可以看做是字符数组
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
String s1 = new String();
System.out.println("s1:" + s1);
System.out.println("s1.length():" + s1.length());

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

byte[] b = {97,98,99,100};
String s2 = new String(b);
System.out.println("s2:" + s2);
System.out.println("s2.length():" + s2.length());

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

String s3 = new String(b,1,2);
System.out.println("s3:" + s3);
System.out.println("s3.length():" + s3.length());

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

char[] c = {'a','b','c','d','权'};
String s4 = new String(c);
System.out.println("s4:" + s4);
System.out.println("s4.length():" + s4.length());

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

String s5 = new String(c,1,2);
System.out.println("s5:" + s5);
System.out.println("s5.length():" + s5.length());

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

String s6 = new String("abcd");
System.out.println("s6:" + s6);
System.out.println("s6.length():" + s6.length());

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

String s7 = "abcd";
System.out.println("s7:" + s7);
System.out.println("s7.length():" + s7.length());
}

}