java中包装类

包装类的分类

int — Integer
char — Charater
long — Long
short — Short
float — Float
double — Double
byte — Byte
boolean — Boolean

继承关系

代码

 // 1.int 类型
        int int1 = 10;
        Integer int2 = int1;
        Integer int3 = Integer.valueOf(int1);
        int int4 = int2;
        int int5 = int3.intValue();

        // 2.char 类型
        char char1 = '2';
        Character char2 = char1;
        Character char3 = Character.valueOf(char1);
        char char4 = char2;
        char char5 = char3.charValue();

        // 3.byte
        byte byte1 = 1;
        Byte byte2 = byte1;
        Byte byte3 = Byte.valueOf(byte1);
        byte byte4 = byte2.byteValue();
        byte byte5 = byte3.byteValue();

        // 4.long
        long long1 = 1234L;
        Long long2 = long1;
        Long long3 = Long.valueOf(long1);
        long long4 = long2;
        long long5 = long3.longValue();


        // 5.short
        short short1 = 12;
        Short short2 = short1;
        Short short3 = Short.valueOf(short1);
        short short4 = short2;
        short short5 = short3.shortValue();

        // 6.boolean
        boolean boolean1 = true;
        Boolean boolean2 = boolean1;
        Boolean boolean3 = Boolean.valueOf(boolean1);
        boolean boolean4 = boolean2;
        boolean boolean5 = boolean3.booleanValue();

        // 7.float
        float float1 = 1.1f;
        Float float2 = float1;
        Float float3 = Float.valueOf(float1);
        float float4 = float2;
        float float5 = float3.floatValue();

        // 8.double
        double double1 = 1.0D;
        Double double2 = double1;
        Double double3 = Double.valueOf(double1);
        double double4 = double2;
        double double5 = double3.doubleValue();

        //String 类型和基本数据类型之间转换
        // 8 种基本数据类都可以转换成 String 类型
        String intStr1 = String.valueOf(int1);
        String charStr1 = String.valueOf(char1);
        String byteStr1 = String.valueOf(byte1);
        String longStr1 = String.valueOf(long1);
        String shortStr1 = String.valueOf(short1);
        String booleanStr1 = String.valueOf(boolean1);
        String floatStr1 = String.valueOf(float1);
        String doubleStr1 = String.valueOf(double1);

        // 包装类转为 String 类型
        String intStr2 = String.valueOf(int2);
        String charStr2 = String.valueOf(char2);
        String byteStr2 = String.valueOf(byte2);
        String longStr2 = String.valueOf(long2);
        String shortStr2 = String.valueOf(short2);
        String booleanStr2 = String.valueOf(boolean2);
        String floatStr2 = String.valueOf(float2);
        String doubleStr2 = String.valueOf(double2);

        // String 转成 基本数据类型 ---> 包装类名.parseXXX(字符串)
        String string = "12sdf";
        int intStr3 = Integer.parseInt(string);
        //char charStr2 = Character. 字符串不能转为字符型
        byte byteStr3 = Byte.parseByte(string);
        long longStr3 = Long.parseLong(string);
        short shortStr3 = Short.parseShort(string);
        boolean booleanStr = Boolean.parseBoolean(string);
        float floatStr = Float.parseFloat(string);
        double doubleStr = Double.parseDouble(string);