在字符串连接中使用原始数据类型的值的字符串表示形式

public class Main {

  public static void main(String[] args) {

    boolean b1 = true; 

    boolean b2 = false; /** n o w    j a v a  . c o m 提 供 **/

    int num = 365; 

    double d = -0.0; 

    char c = 'A'; 

    String str1; 

    String str2 = null; 

      

    str1 = b1 + " friends";  // Assigns "true friends" to str1

    System.out.println(str1);

    str1 = b2 + " identity"; // Assigns "false identity" to str1 /** N o w J a v a . c o m - 时代Java 提供 **/

    System.out.println(str1);

    // Assigns "null and void" to str1. Because str2 is null, it is replaced 

    // by a string "null" by the concatenation operator 

    str1 = str2 + " and void"; 

    System.out.println(str1);

    str1 = num + " days"; // Assigns "365 days" to str1 

    System.out.println(str1);

    str1 = d + " zero";   // Assigns "-0.0 zero" to str1 

    System.out.println(str1);

    

    str1 = Double.NaN + " is absurd"; // Assigns "NaN is absurd" to str1 

    System.out.println(str1);

    

    str1 = c + " is a letter"; // Assigns "A is a letter" to str1

    System.out.println(str1);

    str1 =