Programming Practice: String Concatenation

Given the following code:

String str1, str2, str3, str4;

str1 = "one";
str2 = str1;
str1 = str1 + "two";
System.out.println(str1 + " : " + str2);

str1 = "number" + 8;
str2 = 8 + "number";
str3 = "number" + 1 + 2;
str4 = 1 + 2 + "number";
System.out.println(str1 + '\n' + str2 + '\n' + str3 + '\n' + str4);

char ch = 'A' + 'B' + 'C';
System.out.println("character ch is " + ch);

What is printed out?