# 1.实验内容 ## 1.1 包装类 Java为每个基本类型都提供了包装类

原始类型	包装类
byte	Byte
short	Short
int	Integer
char	Character
float	Float
double	Double
boolean	Boolean

### 1.1.1 Integer类下面列举一下Integer类的常用方法 ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/357390/1501225085417.png-wm) 代码示例 ``` public class IntegerPractice { public static void main(String[] args) { //创建value表示的Integer对象 Integer i1 = new Integer(1); //将s按照10进制转换为Integer对象 Integer i2 = new Integer("10"); //Integer erroInt = new Integer("10md");无法解析,抛异常 //Integer erroInt1 = new Integer("999999999999999999");超过整数能表示的范围,抛异常 //当String不可以解析为整数,抛出NumberFormatException异常 //intValue()方法使用 int intValue = i1.intValue();//intValue = 1 //byteValue()方法使用 byte byteValue = i2.byteValue();//byteValue = 10 //shortValue()方法使用 short shortValue = i1.shortValue();//shortValue = 1 //longValue()方法使用 long longValue = i1.longValue();//longValue = 1 //doubleValue()方法使用 double doubleValue = i1.doubleValue();//doubleValue = 1.0 //floatValue()方法使用 float floatValue = i1.floatValue();//floatValue = 1.0 //compareTo(Integer anotherInteger)方法使用 int compare = i1.compareTo(i2);//compare = -1 //valueOf(String str)用法 Integer value = Integer.valueOf("-10");//value = -10 //Integer i3 = Integer.valueOf("-10s");无法解析,抛异常 //Integer i4 = Integer.valueOf("999999999999999");数值超出范围,抛异常 //equals(Object obj)用法 boolean equal = i1.equals(i2);//equal = false } } ``` ### 1.1.2 Character类 Character 类在对象中包装一个基本类型 char 的值。Character 类型的对象包含类型为 char 的单个字段下面列举Character类的常用方法 ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/357390/1501668330885.png-wm) 代码示例 ``` package JavaLang; public class CharacterPractice { public static void main(String[] args) { char c1 = '1'; boolean isDigit = Character.isDigit(c1);// isDigit = true char c2 = 'A'; boolean isLetter = Character.isLetter(c2);// isLetter = true boolean isLowerCase = Character.isLowerCase(c2);// isLowerCase = false boolean isUpperCase = Character.isUpperCase(c2);// isUpperCase = true char c3 = ' '; boolean isWhiteSpace = Character.isWhitespace(c3);// isWhiteSpace = true boolean isUnicodeIdentifierStart = Character.isUnicodeIdentifierStart(c2);// isUnicodeIdentifierStart = true System.out.println(isUnicodeIdentifierStart); } } ``` ### 1.1.3 Boolean类 Boolean 类将基本类型为 boolean 的值包装在一个对象中。一个 Boolean 类型的对象只包含一个类型为 boolean 的字段。下面列举Boolean类常用的方法 ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/357390/1501670005002.png-wm) 代码示例 ``` package JavaLang; public class BooleanPractice { public static void main(String[] args) { //构造方法示例 Boolean trueBoo = new Boolean("true");// boo = true,不建议使用 Boolean falseBoo = new Boolean("hello"); //falseBoo = false Boolean valueOfBoolean = Boolean.valueOf(true);// valueOfBoolean = true，建议使用 Boolean valueOfString = Boolean.valueOf("true");//valueOfString = true boolean equalsValue = trueBoo.equals(falseBoo);// equlasValue = false Boolean parseBoolean = Boolean.parseBoolean("yes");// parseBoolean = false String toStringValue = falseBoo.toString();// toStringValue = "false" System.out.println(toStringValue); } } ``` ### 1.1.4 String类使用 String 类来定义一个字符串。字符串是常量，它们的值在创建之后不能更改。字符串缓冲区支持可变的字符串。下面列举String类常用的方法 ![图片描述](https://dn-simplecloud.shiyanlou.com/uid/357390/1501756814219.png-wm) 代码示例 ``` package JavaLang; public class StringPractice { public static void main(String[] args) { //初始化化 String str = "helloShiYanLou";//或者String str = new String("helloShiYanLou"); //length() int lengthValue = str.length();//lengthValue = 14 //equals(String str)、equalsIgnoreCase(String str) String str1 = "HELLOSHIYANLOU"; boolean equalsValue = str.equals(str1);//equalsValue = false boolean equalsIgnoreCase = str.equalsIgnoreCase(str1);//equalsIgnoreCase = true //concat(String str) String concatValue = str.concat(str1);//concatValue = "helloShiYanLouHELLOSHIYANLOU" //通常使用+号进行拼接 String concatValue1 = str + str1;//concatValue1 = "helloShiYanLouHELLOSHIYANLOU" //charAt(int index) char ch = str.charAt(1);//ch = 'e' //indexOf(int ch) int index = str.indexOf('l');// index = 2 int index1 = str.indexOf("Z");// index1 = -1 //indexOf(String str) int index2 = str.indexOf("ShiYa");// index2 = 5 int index3 = str.indexOf("nihao");// index3 = -1 //lastIndexOf(int ch) int index4 = str.lastIndexOf('l');// index4 = 3 //lastIndexOf(String str) String str3 = "helloyouhello"; int index5 = str3.lastIndexOf("ll");//index5 = 10 //substring(int begin,int end)、substring(int index) String subString = str3.substring(0, 4);// subString = "hell" String subString1 = str3.substring(1);// subString1 = "elloyouhello"; //trim() String str4 = " hello you "; String trim = str4.trim();// trim = "hello you" System.out.println(trim); } } ```

“JDK 核心 API”实验报告