Java数据类型和变量详解

byte a = 10;
System.out.println(Byte.MAX_VALUE);//输出最大值
System.out.println(Byte.MIN_VALUE);//最小值

short b = 20;
System.out.println(Short.MAX_VALUE);
System.out.println(Short.MIN_VALUE);

int c = 100;
System.out.println(Integer.MAX_VALUE);
System.out.println(Integer.MIN_VALUE);

long d = 10L;//为了区分int和long，long一般加一个大写L
System.out.println(Long.MAX_VALUE);
System.out.println(Long.MIN_VALUE);

float e = 1.1f;//默认是double类型，为了区分就加一个f,F也行
System.out.println(Float.MAX_VALUE);
System.out.println(Float.MIN_VALUE);

int a = 1;
int b = 2;
System.out.println(a/b);//输出0
double c = 1.0;
double d = 2.0;
System.out.println(c/d);//输出0.5

char c1 = '我';
System.out.println(c1);

int a = 100;
long b = 10L;
b = a;//可以把小的赋给大的
a = b;//报错

int a = 100;
long b = 10L;
a = (int)b;//强制类型转换会丢失数据
byte b1 = 100;//100默认为int，没有超过byte的范围，隐式转换
byte b2 = (byte)257;//257默认为int，超过了范围,需要强转

int a = 10;
long b = 20L;
a = a+b;//报错,int提升为long，最后a+b的类型是long,不能赋给int
a += b;
System.out.println(a);//输出50

byte a = 10;
byte b = 20;
byte c = a + b; //编译出错
System.out.println(c);

byte a = 10;
byte b = 20;
byte c = (byte)(a + b); 
System.out.println(c);

String s1 = "hello";
String s2 = "world";
System.out.println(s1+s2);//helloworld
//字符串可以拼接在一起

int a = 10;
String s1 = a + "";
String s2 = String.valueOf(a);

String s3 = "10";
int num = Integer.parseInt(s3);