Java StringJoiner merge()方法

StringJoiner的 merge(StringJoiner other) 如果是非空的，会添加给定的StringJoiner的内容，不含前缀和后缀，作为下一个元素。如果给定的StringJoiner是空的，该调用没有效果。

语法：

public StringJoiner merge(StringJoiner other)

参数： 该方法接受一个强制性参数 ， 即StringJoiner，其内容应被合并到该方法中

返回： 该方法返回该StringJoiner

异常： 如果其他StringJoiner为空，该方法会抛出 NullPointerException

以下程序说明merge()方法：

示例1： 演示用分隔符” “合并

// Java program to demonstrate
// merge() method of StringJoiner
 
import java.util.StringJoiner;
 
public class GFG {
    public static void main(String[] args)
    {
 
        // Creating StringJoiner with delimiter " "
        StringJoiner str1 = new StringJoiner(" ");
 
        // Adding elements in the StringJoiner
        str1.add("Geeks");
        str1.add("for");
        str1.add("Geeks");
 
        // Print the StringJoiner
        System.out.println("StringJoiner 1: "
                           + str1.toString());
 
        // Creating the second StringJoiner
        StringJoiner str2 = new StringJoiner(" ");
 
        str2.add("A");
        str2.add("Computer");
        str2.add("Portal");
 
        // Print the second StringJoiner
        System.out.println("StringJoiner 2: "
                           + str2.toString());
 
        // Merging the StringJoiner using merge()
        StringJoiner str = str1.merge(str2);
 
        // Printing the merged StringJoiner
        System.out.println("Merged StringJoiner : "
                           + str);
    }
}

输出

StringJoiner 1: Geeks for Geeks
StringJoiner 2: A Computer Portal
Merged StringJoiner : Geeks for Geeks A Computer Portal

例子2： 演示带有分隔符”，”的merge()

// Java program to demonstrate
// merge() method of StringJoiner
 
import java.util.StringJoiner;
 
public class GFG1 {
    public static void main(String[] args)
    {
 
        // Creating StringJoiner with delimiter ", "
        StringJoiner str1 = new StringJoiner(", ");
 
        // Adding elements in the StringJoiner
        str1.add("Geeks");
        str1.add("for");
        str1.add("Geeks");
 
        // Print the StringJoiner
        System.out.println("StringJoiner 1: "
                           + str1.toString());
 
        // Creating the second StringJoiner
        StringJoiner str2 = new StringJoiner(", ");
 
        str2.add("A");
        str2.add("Computer");
        str2.add("Portal");
 
        // Print the StringJoiner
        System.out.println("StringJoiner 2: "
                           + str2.toString());
 
        // Merging the StringJoiner using merge()
        StringJoiner str = str1.merge(str2);
 
        // Printing the merged StringJoiner
        System.out.println("Merged StringJoiner : "
                           + str);
    }
}

输出

StringJoiner 1: Geeks, for, Geeks
StringJoiner 2: A, Computer, Portal
Merged StringJoiner : Geeks, for, Geeks, A, Computer, Portal

例3： 演示NullPointerException

// Java program to demonstrate
// merge() method of StringJoiner
 
import java.util.StringJoiner;
 
public class GFG1 {
    public static void main(String[] args)
    {
 
        // Creating StringJoiner with delimiter ", "
        StringJoiner str1 = new StringJoiner(", ");
 
        // Adding elements in the StringJoiner
        str1.add("Geeks");
        str1.add("for");
        str1.add("Geeks");
 
        // Print the StringJoiner
        System.out.println("StringJoiner 1: "
                           + str1.toString());
 
        // Creating the second StringJoiner
        // to be merged as null
        StringJoiner str2 = null;
 
        // Print the StringJoiner
        System.out.println("StringJoiner 2: "
                           + str2);
 
        try {
 
            // Merging the StringJoiner using merge()
            StringJoiner str = str1.merge(str2);
        }
        catch (Exception e) {
            System.out.println("Exception during merge: "
                               + e);
        }
    }
}

输出

StringJoiner 1: Geeks, for, Geeks
StringJoiner 2: null
Exception during merge: java.lang.NullPointerException