public class changetype {

     public static void main(String[] args)

     {

        String ar = "true";  //String转 boolean ,只要不是"true",结果即为false;

        boolean ar1 = Boolean.parseBoolean(ar);

        if(ar1)

        {

            System.out.println("true");   //结果为true;

        }

        String str = "12";    //String 转   int

        int m = Integer.parseInt(str);

        System.out.println(m);

        String str0 = "12.6";             //string转换成double

        double x = Double.parseDouble(str0);

        System.out.println(x);

        int y = 5;

        String str1 = y+"";

        System.out.println(str1);

        int flag = 100;         //int转String,任何类型与字符串连接将变为字符串类型。不推荐使用

        String a = flag+"";

        System.out.println(a); 

        int flag0 = 200;               //int 转String 利用String.valueOf();

        String str3 = String.valueOf(flag0);

        System.out.println(str3);

        float h = 12.6f;  //  float 转 int ，由高到低必须进行强制类型转换，损失精度变为12

        int w =(int)h;

        System.out.println(w);    //结果为12

        float c = 89.6666f;

        double s = c;

        System.out.println(s);    //结果为89.666677987979

        double e = 78.999999999;

        float o = (float)e;

        System.out.println(o);   //结果为79

     }}