java基础2

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1.数据类型

package DataType;

import java.util.Scanner;

public class DataType {

public static void main(String[] args) {
// TODO Auto-generated method stub

  int a = 1;
  long b = 2L;
  float c = 3.1f;
  double d = 4.2d;
  boolean e = true;
  System.out.println("boolean = " + e);
  //手动输入boolean值判断输出
  Scanner sc = new Scanner(System.in);
  //把输入的boolean值提到上面设置成变量
  boolean flag = sc.nextBoolean();

  if(flag==true){
   System.out.println("int a = " + a);
   System.out.println("输入的boolean值 = " + flag);

  }else{
   System.out.println("float b = " + b);
   System.out.println("输入的boolean值 = " + flag);
  }

  System.out.println(b+2);
  System.out.println(c);
  System.out.println(d);
  //字符
  char h = 's';
  System.out.println("char = " + h);
  //字符串
  String str ="solo";
  System.out.println("str = " + str);


  String str1 = "12";
  //把String类型的数据强制转换成int型
  int in = Integer.parseInt(str1);
  System.out.println("in = "+ (in + 3));
  //把int型强制转换成String型
  String str2 = in + "";
  System.out.println("str2 = "+ (str2 + 3));
}

}

2.方法调用和数据类型强制转换package DataType;

public class DemoVar {

int i = 2;
public void test(){

  System.out.println(i);
}

public void test1(){

  int i = 3;
  System.out.println(i);
}

public String add(int a,String str){
  //会强制转换成String类型
  return str + a;
}

public static void main(String[] args) {
  // TODO Auto-generated method stub

  DemoVar demo = new DemoVar();
  //方法调用
  demo.test();
  demo.test1();

  String result = demo.add(1, "abc");
  System.out.println(result);
  //相当于System.out.println("abc" + 1); 输出abc1

}

}

3.方法重载

package DataType;

public class reload {

public static void main(String[] args) {
  // TODO Auto-generated method stub
  int i;
  double t;
  String str1;
  reload rad = new reload();
  i = rad.add(1, 2);
  System.out.println(i);
  i = rad.add(2, 3, 4);
  System.out.println(i);
  t = rad.add(1.2, 2.3);
  System.out.println(t);
  str1 = rad.add(7, "hello");
  System.out.println(str1);

}

public int add(int x,int y){
  return x+y;
}
public int add(int x,int y,int z){
  return x+y+z;
}
public double add(double x,double y){
  return x+y;
}
public String add(int x, String str){
  return x+str;
}
}

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